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Reductionism

Reductionism is a foundational approach in philosophy and science that posits complex systems, phenomena, or entities can be fully understood and explained by analyzing their simpler, constituent parts or underlying fundamental principles, often assuming that higher-level properties emerge solely from interactions at lower levels.^[1] This view encompasses multiple dimensions, including ontological reductionism, which asserts that wholes are nothing more than the sum of their minimal parts, and methodological reductionism, which advocates explaining complex wholes through the study of smaller entities or processes.^[2] In scientific contexts, such as biology and physics, reductionism has driven major advances, like elucidating molecular mechanisms of disease through genetic analysis, but it is distinguished from holism by its emphasis on decomposition over integration.^[1] Key variants include epistemological reductionism, which holds that knowledge in one domain (e.g., biology) can be derived from or reduced to knowledge in a more fundamental domain (e.g., physics or chemistry), maintaining distinct disciplines while linking them hierarchically.^[1] Proponents argue this method enables precise, predictive models; for instance, in microbiology, reductionist techniques like mutagenesis have identified genes essential for bacterial infection.^[1] However, reductionism faces significant critiques for oversimplifying non-linear interactions and emergent properties that cannot be predicted from parts alone, as seen in biological systems where whole-organism behaviors defy isolated component analysis.^[3] Critics like Ernst Mayr contend that while reductionism excels at basic mechanisms, it neglects the holistic, historical, and functional contexts unique to fields like evolutionary biology.^[3] Despite these limitations, reductionism remains influential across disciplines, informing debates in philosophy of mind, where it challenges dualism by proposing mental states reduce to physical brain processes, and in systems theory, where it contrasts with approaches addressing "dark systems" of hidden properties.^[2] Recent scholarship emphasizes complementary integration with holistic methods, such as systems biology, which combines reductionist data with network analyses to capture emergent dynamics more effectively.^[1] This ongoing tension underscores reductionism's role as both a powerful tool and a contested paradigm in understanding complexity.

Core Concepts

Definition and Principles

Reductionism is a philosophical thesis asserting that complex systems, phenomena, or entities can be fully understood and explained by analyzing them in terms of their simpler, more basic constituents or underlying laws.^[4] This approach emphasizes breaking down wholes into parts to uncover the fundamental mechanisms driving observed behaviors, positing that higher-level descriptions are ultimately derivable from or reducible to lower-level ones.^[5] At its core, reductionism operates through two primary principles: explanatory reduction and metaphysical reduction. Explanatory reduction focuses on the epistemic process of deriving explanations for higher-level phenomena from more fundamental theories, laws, or mechanisms, often involving deductive or bridging arguments to connect levels of description.^[6] Metaphysical reduction, by contrast, makes an ontological claim that higher-level entities or properties are nothing over and above their lower-level components, denying any independent existence or emergent qualities beyond the sum of the parts.^[7] Ontological reductionism serves as a subtype of metaphysical reduction, specifically emphasizing that reality's composition consists solely of basic entities without irreducible wholes.^[1] The practical mechanisms of reductionism typically involve three interrelated steps: decomposition, where a complex system is divided into its elemental parts; analysis, which examines the properties and interactions of those parts; and reconstruction, whereby the system is reassembled conceptually to verify that the whole's behavior emerges predictably from the parts' dynamics.^[4] These steps aim to eliminate mystery by grounding explanations in verifiable, simpler truths, assuming no novel properties arise that cannot be accounted for at the foundational level.^[5] This perspective stands in opposition to holism, which contends that complex wholes possess properties irreducible to their components, requiring study of the integrated system rather than isolated analysis.^[1]

Historical Development

The roots of reductionist thought trace back to ancient Greek philosophy, particularly the atomist theories developed by Leucippus and his student Democritus in the 5th century BCE. Leucippus, a Greek philosopher active in the 5th century BCE, proposed that the universe consists of indivisible particles—atoms—moving through a void, reducing all phenomena to the interactions of these fundamental units without invoking divine or supernatural causes.^[8] Democritus expanded this framework, arguing that complex entities like organisms and societies emerge solely from the mechanical combinations of atoms differing only in shape, size, and arrangement, thereby laying the metaphysical groundwork for explaining reality through simpler constituents.^[8] During the medieval period, reductionist ideas remained marginal amid dominant Aristotelian and theological frameworks, but they resurfaced in the early modern era through mechanistic philosophy. René Descartes (1596–1650) advanced a corpuscular view of matter in works like Principia Philosophiae (1644), positing that the physical world operates as a machine governed by local contacts and motions of extended particles, reducing natural phenomena to basic mechanical principles and excluding occult qualities.^[9] This approach influenced Isaac Newton's Philosophiæ Naturalis Principia Mathematica (1687), where the laws of motion and universal gravitation provided a mathematical foundation for reducing diverse physical events— from planetary orbits to terrestrial mechanics—to interactions among particles under simple, universal rules. The Enlightenment era marked a pivotal shift from metaphysical reductionism, focused on ultimate ontological components, to methodological reductionism, emphasizing empirical decomposition in scientific inquiry. Thinkers like Francis Bacon and members of the Royal Society promoted breaking complex systems into observable parts for experimentation, aligning with the era's valorization of reason and mechanism over speculation.^[4] This transition facilitated the Scientific Revolution's emphasis on testable hypotheses derived from fundamental laws. In the 19th century, Charles Darwin's On the Origin of Species (1859) applied reductionist principles to biology, explaining the diversity and complexity of life through gradual variations and natural selection acting on heritable traits, without recourse to vital forces or design.^[10] By the early 20th century, logical positivism revived reductionism as a tool for unifying science. The Vienna Circle, active in the 1920s and 1930s under Moritz Schlick and Rudolf Carnap, advocated reducing higher-level scientific theories to a foundational physical base, promoting a hierarchical "unity of science" where empirical protocols and logical analysis dissolve complex statements into verifiable atomic facts.^[11] Post-World War II developments introduced significant critiques, tempering earlier enthusiasm for strict reductionism. Philosophers like Karl Popper and Thomas Kuhn highlighted limitations in reducing social or biological sciences to physics, arguing that emergent properties and contextual factors resist full decomposition, leading to more nuanced, pluralistic views in analytic philosophy of science.

Types of Reductionism

Ontological Reductionism

Ontological reductionism posits that complex entities or wholes are ontologically identical to, or exhaustively composed of, their more basic parts, such that higher-level phenomena do not introduce any novel ontological categories beyond aggregates of fundamental constituents.^[12] This view denies the existence of emergent properties that possess independent ontological status, maintaining instead that all reality can be accounted for by a minimal set of basic entities and their arrangements.^[13] A central argument for ontological reductionism is the principle of supervenience, which holds that higher-level properties are determined by and dependent upon lower-level ones, such that no two entities can differ in their higher-level features without differing in their lower-level base.^[14] In physics, this manifests as micro-reduction, where macroscopic objects, such as tables or planets, are ontologically reducible to sums of atoms and subatomic particles governed by fundamental physical laws, with no additional ontological primitives required to explain their existence.^[13] These arguments support a layered ontology where each level supervenes on the one below, culminating in a physicalist foundation. Illustrative examples include the reduction of mental states to brain processes in eliminative materialism, which contends that folk-psychological concepts like beliefs are illusory and should be supplanted by neuroscientific descriptions of neural activity, thereby eliminating any non-physical mental ontology. Similarly, biological organisms are viewed as mere aggregates of molecules and biochemical interactions, with no irreducible vital forces animating life beyond physical compositions.^[12] Philosophically, ontological reductionism distinguishes between token identity, where individual instances (tokens) of higher-level entities are identical to specific lower-level instances (e.g., a particular pain token identical to a specific brain state token), and type identity, where entire categories (types) of higher-level properties correspond to types of lower-level properties (e.g., pain as a type identical to C-fiber firing as a type). This framework challenges substance dualism by rejecting the ontological independence of non-physical minds or souls, arguing instead that all entities, including conscious experiences, supervene on and reduce to physical bases, thereby resolving the mind-body problem through materialist monism.^[14] A specific formulation within ontological reductionism is mereological reduction, which analyzes part-whole relations in metaphysics, asserting that wholes are nothing over and above their parts arranged in certain ways, without surplus ontological structure.^[15] This approach addresses composition by treating complex objects as mereological sums, where the identity of the whole derives strictly from the mereology of its constituents, reinforcing the denial of emergent wholes with independent existence.^[16]

Methodological Reductionism

Methodological reductionism refers to the investigative strategy in science that seeks to explain complex phenomena by breaking them down into simpler components and their interactions, typically through empirical methods such as experimentation and modeling. This approach emphasizes the analysis of systems at lower levels of organization to derive explanations for higher-level behaviors, without committing to metaphysical claims about the ultimate nature of reality.^[1]^[10] Key techniques in methodological reductionism include the decomposition of systems into parts for targeted study, such as dissection in biology to examine organ functions independently, and the isolation of variables in controlled experiments to assess individual causal influences. Bottom-up modeling represents another core method, where basic elements—like particles or genes—are simulated and combined to predict emergent properties of the whole system. These techniques facilitate precise, replicable investigations by minimizing confounding factors and focusing on mechanistic details.^[10]^[17] Representative examples illustrate its application across disciplines. In chemistry, complex reactions are reduced to interactions among atoms and molecules, allowing predictions of outcomes based on quantum mechanics and thermodynamics, as seen in the modeling of reaction kinetics. In biology, genetic analysis reduces heredity to the study of individual genes and their expression, exemplified by experiments isolating DNA sequences to understand trait inheritance, such as in Mendelian genetics extended to molecular levels. These methods enable scientists to build explanatory bridges from micro-level processes to macro-level observations.^[18]^[10] Philosophically, methodological reductionism aligns with the hypothetico-deductive method, where hypotheses about component interactions are formulated and tested against empirical data to refine explanations. It also underpins the unity of science thesis, articulated by Oppenheim and Putnam in 1958, which advocates for a hierarchical structure of sciences where higher-level disciplines are methodologically connected to fundamental physics through successive reductions. This thesis promotes a cohesive scientific framework by encouraging the use of lower-level laws to illuminate broader phenomena.^[19]^[20] A specific role for methodological reductionism appears in Karl Popper's criterion of falsifiability, outlined in his 1934 work Logik der Forschung, where simplifying complex systems into discrete, testable hypotheses enhances the potential for empirical refutation, thereby advancing scientific progress. By reducing broad claims to specific predictions, this approach ensures hypotheses remain amenable to critical testing, distinguishing scientific inquiry from unfalsifiable assertions.^[21]^[22]

Theory Reductionism

Theory reductionism refers to the philosophical idea that a higher-level scientific theory can be reduced to a more fundamental lower-level theory if the laws or statements of the former are logical consequences of the laws of the latter, often facilitated by bridge principles or correspondence rules that link the vocabularies of the two theories. This form of reduction aims to show how explanatory power at one level emerges from mechanisms at a deeper level, providing a unified understanding of natural phenomena. Bridge principles serve as auxiliary assumptions that equate or relate terms from the higher theory (e.g., "temperature") to those in the lower theory (e.g., "average kinetic energy of molecules").^[23] A seminal model for theory reduction was proposed by Ernest Nagel in 1961, framing it as a deductive-nomological explanation. In this model, the laws of the reduced theory are derived from the postulates of the reducing theory combined with correspondence rules that establish equivalences between theoretical terms. For instance, the derivation proceeds as follows: the higher-level laws L_1, \dots, L_m are shown to follow logically from the lower-level laws L'_1, \dots, L'_n and bridge statements C_1, \dots, C_r, such that (L'_1 \land \dots \land L'_n \land C_1 \land \dots \land C_r ) \vdash L_1 \land \dots \land L_m. This approach emphasizes logical derivability while accommodating cases where the reduced theory's assumptions are approximately preserved in the limit of the reducing theory.^[23] Prominent examples illustrate this process. In physics, thermodynamics is reduced to statistical mechanics, where macroscopic laws like the ideal gas law PV = nRT emerge from the microscopic behavior of particles governed by the Maxwell-Boltzmann distribution. The derivation begins with the average kinetic energy of gas molecules: for a monatomic ideal gas, the equipartition theorem yields \frac{1}{2} m \langle v^2 \rangle = \frac{3}{2} kT, where m is the molecular mass, \langle v^2 \rangle is the mean square speed, k is Boltzmann's constant, and T is temperature, so \langle \frac{1}{2} m v^2 \rangle = \frac{3}{2} kT. Pressure arises from momentum transfer during wall collisions: for molecules hitting a wall of area A perpendicular to the x-direction, the change in momentum per collision is $2mv_x, and the number of collisions per unit time is \frac{1}{2} N \langle v_x \rangle / V (with N/V density and averaging over directions), leading to P = \frac{1}{3} (N/V) m \langle v^2 \rangle. Substituting the kinetic energy relation gives P = \frac{NkT}{V}, or equivalently PV = nRT for n = N / N_A moles and R = N_A k. Another example is the partial reduction of classical genetics to molecular biology, where Mendelian laws (e.g., segregation and independent assortment) are explained by DNA replication and recombination mechanisms, though requiring intertheoretic mappings rather than strict deduction due to the complexity of gene expression.^[24]^[25] Despite these successes, theory reduction faces significant challenges, particularly from multiple realizability, which posits that a single higher-level phenomenon or law can be instantiated by diverse lower-level mechanisms. This undermines the universality of bridge principles, as they would need to encompass disjunctive realizations (e.g., a psychological state realized by neural patterns in humans, silicon circuits in machines, or biochemical processes in aliens), rendering derivations non-explanatory or overly complex. Philosophers like Hilary Putnam and Jerry Fodor argued that such multiplicity preserves the autonomy of higher-level theories, preventing full reduction while still allowing explanatory relations.^[26]

Applications in Disciplines

In Science

Reductionism in science manifests through efforts to explain complex phenomena by deriving them from simpler, more fundamental components and laws, particularly in the physical, chemical, and biological domains. In physics, quantum mechanics provides a foundational reduction of classical mechanics, where macroscopic behaviors emerge as limiting cases of quantum principles under conditions of large quantum numbers or high energies.^[27] This reduction is not exact but approximate, allowing classical predictions to align with quantum ones in the appropriate regime.^[28] Similarly, particle physics advances reductionism by unifying fundamental forces; the electroweak theory merges electromagnetic and weak interactions into a single framework at high energies, while the Standard Model further incorporates the strong force through quantum chromodynamics, portraying diverse interactions as manifestations of underlying gauge symmetries.^[29] In chemistry, molecular orbital theory exemplifies reductionism by interpreting chemical reactions and bonding as consequences of electron behaviors governed by quantum mechanical wavefunctions. Developed in the 1920s and 1930s by physicists like Friedrich Hund and Robert Mulliken, this approach constructs molecular properties from atomic orbitals, reducing macroscopic reactivity—such as bond formation or dissociation—to probabilistic electron distributions and energy minimizations.^[30] This framework has enabled precise predictions of molecular spectra and reaction pathways, bridging chemistry to quantum physics without invoking emergent properties unique to chemical scales.^[31] Biology has seen profound reductionist successes through the identification of DNA as the fundamental unit of heredity, as proposed in the Watson-Crick double-helix model of 1953, which explains genetic information storage and replication via base-pairing rules derivable from molecular structure.^[32] In neuroscience, reductionism seeks to account for behavior by mapping it to patterns of neural firings, positing that cognitive processes and actions arise from electrochemical signals in neuron networks, as evidenced by techniques like optogenetics that manipulate specific firings to elicit behavioral responses.^[33] These approaches align with theory reductionism, where higher-level biological theories are linked to and partially derived from lower-level physical and chemical ones.^[34] Key successes of scientific reductionism include its predictive power, such as in protein folding, where quantum chemistry principles—applied through density functional theory—allow simulations to forecast three-dimensional structures from amino acid sequences, achieving accuracies that guide drug design and enzyme engineering.^[35] A landmark illustration is the 2012 discovery of the Higgs boson at CERN's Large Hadron Collider, which confirmed the Higgs mechanism and reduced the origin of particle masses to interactions with the pervasive Higgs field, unifying mass generation within the Standard Model.^[36] Despite these advances, reductionism faces limitations in biology, where quantum effects persist at macroscopic scales, as in photosynthesis, where coherent energy transfer among chlorophyll molecules exploits quantum superposition to achieve near-perfect efficiency, defying purely classical explanations and suggesting irreducible quantum influences on biological function.^[37] Such phenomena highlight that while reductionist strategies excel in isolating mechanisms, they sometimes overlook holistic quantum dynamics essential for emergent efficiencies in living systems.^[38]

In Mathematics and Computer Science

In mathematics, reductionism manifests through the effort to derive complex theorems from a minimal set of axioms or postulates, establishing a foundational hierarchy where higher-level structures emerge from basic primitives. A seminal example is Euclidean geometry, where David Hilbert formalized the system by reducing geometric propositions to a rigorous set of 20 axioms and one axiom schema, building upon Euclid's original five postulates to ensure consistency and completeness within the axiomatic framework. This approach demonstrates how intricate spatial relationships, such as congruence and similarity, can be logically deduced from undefined terms like "point" and "line," avoiding gaps in Euclid's original formulation.^[39] Set theory exemplifies foundational reductionism by positing sets as the sole primitive from which all mathematical objects—numbers, functions, and spaces—are constructed. Zermelo-Fraenkel set theory (ZF), refined in the early 20th century, achieves this by axiomatizing set membership and operations, enabling the encoding of arithmetic, analysis, and topology within a unified system; for instance, natural numbers are defined via the von Neumann ordinals, reducing Peano arithmetic to set-theoretic constructions.^[39] This reductionist strategy underpins modern mathematics, as ZF provides a consistent basis for deriving theorems across disciplines without invoking additional primitives.^[40] In computer science, reductionism appears in modular programming, where complex software systems are decomposed into independent, reusable modules or functions, each handling a specific task while minimizing interdependencies. Edsger Dijkstra's structured programming paradigm, introduced in the late 1960s, embodies this by advocating decomposition into hierarchical blocks—sequences, selections, and iterations—reducing program complexity and enhancing verifiability, as seen in languages like Pascal that enforce such modularity.^[41] This approach aligns with reductionist principles by breaking monolithic code into verifiable subunits, facilitating debugging and maintenance without altering the overall system's behavior.^[42] Computational complexity theory employs reductions to classify problems by transforming one into another via efficient algorithms, revealing inherent difficulties. Polynomial-time reductions, central to defining NP-completeness, allow showing that if one problem is solvable in polynomial time, so are others reducible to it; for example, the traveling salesman problem reduces to the Hamiltonian cycle problem, establishing shared hardness.^[43] The Cook-Levin theorem (1971) solidifies this by proving Boolean satisfiability (SAT) is NP-complete, as any nondeterministic Turing machine verification can be encoded as a polynomial-size Boolean formula, making SAT a universal target for reductions from all NP problems.^[44] Exemplifying reduction in computation, Alan Turing's 1936 model of the Turing machine reduces all effective calculability to operations on a tape with a read-write head, finite states, and a symbol alphabet, proving that any algorithmic process can be simulated by such a device.^[45] Algorithm design paradigms like divide-and-conquer further illustrate this, recursively partitioning problems into subproblems, solving them independently, and combining results; merge sort, for instance, halves an array, sorts subarrays, and merges in linear time, reducing sorting complexity from quadratic to O(n \log n).^[46] However, reductionism faces limits in formal systems, as revealed by Kurt Gödel's incompleteness theorems (1931), which demonstrate that any consistent axiomatic system capable of expressing basic arithmetic contains undecidable propositions—statements neither provable nor disprovable within the system—thus bounding the reductive power of axioms to capture all truths. These theorems highlight that while reductions can formalize vast domains, inherent incompleteness prevents total encapsulation of mathematical reality in finite axiom sets.^[47]

In Philosophy and Religion

In philosophy, reductionism has played a central role in debates concerning the nature of the mind, particularly through the identity theory, which posits that mental states are identical to physical brain processes. This view was notably advanced by U.T. Place in his 1956 paper, where he argued that consciousness could be reasonably hypothesized as a brain process, drawing on phenomenological and neurophysiological evidence to support the reduction of sensory experiences to neural events.^[48] Ontological reductionism underpins such materialist perspectives by asserting that higher-level mental phenomena are ultimately reducible to fundamental physical entities.^[49] Ethical naturalism represents another application of reductionism in philosophy, seeking to reduce moral properties and facts to natural properties observable through empirical science, such as biological or psychological states. Proponents like William K. Frankena have defended this approach by arguing that ethical terms can be analyzed in terms of natural predicates, thereby integrating morality into the broader framework of naturalistic inquiry without invoking supernatural or non-natural elements.^[50] In religious contexts, reductionism manifests in materialist interpretations that explain spiritual experiences as products of brain activity, challenging traditional views of the soul or divine encounters. Neurophilosophical analyses, for instance, have proposed that religious visions or mystical states arise from specific neural firings, reducing what believers perceive as transcendent to physiological mechanisms.^[51] Theological critiques of such reductions emphasize a synthesis of faith and reason, as articulated by Thomas Aquinas in his Summa Theologica, where he integrated Aristotelian philosophy with Christian doctrine to affirm that divine truths transcend purely rational or material explanations while remaining compatible with them.^[52] Sigmund Freud's psychoanalytic framework exemplifies reductionist approaches to religion, portraying religious beliefs as illusions fulfilling psychological needs for protection and wish-fulfillment, akin to childhood dependencies on parental authority. In The Future of an Illusion (1927), Freud systematically dismantled religious doctrines by tracing them to unconscious drives and societal neuroses, advocating for science as a substitute. Similarly, Richard Dawkins in The God Delusion (2006) employs evolutionary biology to reduce religious faith to adaptive byproducts of cognitive mechanisms shaped by natural selection, such as agency detection and pattern-seeking behaviors that once aided survival but now foster theistic illusions. A key philosophical debate involves the reduction of the soul to bodily processes, particularly in critiques of René Descartes' substance dualism, which posits the mind (or soul) as a non-extended, thinking substance distinct from the extended body. Critics like Anne Conway argued that this sharp dualism leads to an untenable mechanism, where vital spiritual aspects are erroneously separated from corporeal reality, advocating instead for a monistic vitalism that unifies body and soul without reductive elimination.^[53] During the Enlightenment, deism emerged as a reductionist theological movement, portraying God as a distant first cause who set the universe in motion according to rational laws but refrained from ongoing intervention. Thinkers such as Matthew Tindal in Christianity as Old as the Creation (1730) exemplified this by equating divine providence with natural order, stripping away miraculous revelations and reducing religion to a deistic rationalism aligned with Newtonian mechanics.^[54]

Criticisms and Alternatives

Challenges to Ontological and Methodological Approaches

Critics of ontological reductionism argue that it overlooks downward causation, where higher-level wholes exert causal influence on their constituent parts, thereby challenging the view that all properties and causal relations can be fully explained by lower-level components alone.^[55] This perspective posits that emergent properties at the system level impose constraints that guide the behavior of parts in ways not predictable from part-level descriptions, as explored in analyses of holistic systems in philosophy of science.^[56] For instance, in complex adaptive systems, the overall configuration can retroactively shape micro-level interactions, undermining the reductionist assumption of unidirectional bottom-up determination.^[57] A related critique involves mereological fallacies, which occur when properties attributable only to wholes are erroneously ascribed to their parts, such as claiming that the brain "believes" or "intends" rather than the person.^[58] In their 2003 work Philosophical Foundations of Neuroscience, M.R. Bennett and P.M.S. Hacker identify this as a pervasive error in cognitive neuroscience, where brain regions are treated as agents with psychological capacities that logically apply solely to the integrated organism. This fallacy highlights how ontological reductionism distorts conceptual clarity by conflating levels of description, leading to pseudo-explanations that ignore the irreducibly holistic nature of certain phenomena.^[59] Jaegwon Kim's supervenience arguments from the 1980s and 1990s further expose dilemmas in ontological reductionism by examining the relationship between higher-level mental properties and their physical bases. Kim contends that if mental properties supervene on physical ones—meaning no mental difference without a physical difference—yet possess causal efficacy, this leads to overdetermination or exclusion problems, where higher-level causes appear redundant or illusory unless reduced.^[60] His "pairing problem" illustrates how supervenience fails to guarantee the necessary one-to-one mappings for strict ontological reduction, forcing nonreductive physicalists into uncomfortable positions regarding mental causation.^[61] Multiple realizability provides another barrier to ontological reduction, as the same higher-level property can be instantiated by diverse lower-level realizations across different systems, preventing type-type identities essential for reduction.^[62] Originating in Hilary Putnam's and Jerry Fodor's work in the 1960s and 1970s, this argument demonstrates that psychological states, for example, can be realized by varied neural structures in humans, silicon-based processors in machines, or even alien physiologies, rendering universal reductive laws untenable.^[63] Similar issues arise in theory reductionism, where abstract principles face analogous realizability challenges.^[62] Turning to methodological reductionism, challenges arise from the practical limits of decomposition in systems exhibiting chaos, where sensitivity to initial conditions amplifies small variations into unpredictable outcomes, complicating efforts to analyze parts in isolation.^[64] In chaotic dynamics, as described by the Lorentz attractor model, even precise knowledge of components fails to yield reliable whole-system predictions without holistic contextual integration, thus questioning the efficacy of reductive strategies like isolating subsystems for study.^[64] This sensitivity underscores how methodological reduction can lose predictive and explanatory power in nonlinear regimes, favoring integrative approaches over pure decomposition.^[65] In biology, the concept of irreducible complexity critiques methodological reduction by suggesting that certain molecular systems require all parts to function simultaneously, defying stepwise disassembly and reassembly in evolutionary or analytical terms. Michael Behe introduced this idea in his 1996 book Darwin's Black Box, using examples like the bacterial flagellum, where removing any component abolishes function, implying that reductive analysis cannot reconstruct the system's origin or operation from simpler precursors—though this claim remains highly contested within scientific communities.^[66] The grain argument further undermines both ontological and methodological reductionism by highlighting that explanatory power depends on selecting an appropriate level of detail; reducing to an excessively fine grain overwhelms with irrelevant micro-details, while coarser grains preserve intelligibility but risk oversimplification. As articulated by Michael Lockwood in discussions of physicalism, this "grain problem" reveals that no single reductive level universally captures phenomena, as shifting granularity alters what counts as explanatory, often diminishing the coherence of higher-level narratives. Thus, reductionism's insistence on fundamental levels ignores the context-dependent utility of multiple descriptive grains.^[67]

Issues with Free Will and Causation

Reductionism, particularly in its ontological form assuming physical determinism, poses significant challenges to the concept of free will by suggesting that human decisions are ultimately reducible to deterministic neural processes. In the 1983 experiments conducted by Benjamin Libet and colleagues, participants reported the moment of conscious intention to perform a simple action, such as flexing a finger, while brain activity was monitored via electroencephalography. The results indicated that a readiness potential—a neural signal associated with the preparation of voluntary action—emerged approximately 350 milliseconds before the reported awareness of the intention. While this has been interpreted to imply that unconscious brain processes initiate decisions prior to conscious awareness, supporting a reductionist view of neural determinism where free will appears illusory as actions stem from prior physical causes in the brain rather than autonomous conscious choice, the findings are controversial. Critiques, including those in the cited review, note the triviality of the actions studied and suggest the readiness potential may reflect spontaneous neural fluctuations rather than deterministic initiation; later research, such as a 2023 meta-analysis, argues the evidence is insufficient to undermine free will, particularly for deliberate decisions where no such potential precedes awareness.^[68]^[69] Philosophers have responded to such reductionist challenges by debating compatibilism and incompatibilism regarding free will and determinism. Compatibilists argue that free will is compatible with determinism, defining it as the capacity to act according to one's motivations without external coercion, even if those motivations are determined by prior causes. Daniel Dennett, in his 1984 book Elbow Room: The Varieties of Free Will Worth Wanting, defends this compatibilist reduction by emphasizing that the kind of free will worth wanting involves evolved cognitive competencies that allow for rational deliberation and avoidance of regret, without requiring indeterminism or supernatural intervention.^[70] In contrast, incompatibilists contend that true free will necessitates the ability to have done otherwise in the exact same circumstances, which determinism precludes, rendering moral agency problematic under a strictly reductionist framework.^[71] In terms of causation, reductionism posits a unidirectional chain from micro-level physical events to macro-level phenomena, including human behavior, but this leads to issues of overdetermination where mental causes become redundant. If physical states fully determine outcomes, as in the causal closure principle, then any distinct mental event causing the same effect would overdetermine it unnecessarily, violating parsimony.^[72] This problem manifests in epiphenomenalism, a consequence of failed reductive accounts of the mind, where mental states are mere byproducts of physical processes with no independent causal role in producing actions or further mental states.^[73] Critics argue that such a view undermines the intuitive efficacy of thoughts and intentions, as seen in Jaegwon Kim's exclusion argument, which holds that non-reducible mental properties cannot causally interact with the physical world without either epiphenomenal irrelevance or violation of physical laws.^[74] Quantum indeterminacy, emerging in the 1920s with Werner Heisenberg's uncertainty principle, challenges the strict causal reductionism underlying these debates by introducing fundamental unpredictability at the subatomic level. Heisenberg's 1927 formulation demonstrated that precise simultaneous measurement of position and momentum is impossible, implying inherent limits to deterministic predictions even in principle. This indeterminism disrupts the reductionist chain from micro to macro causation, potentially opening space for non-deterministic influences on neural processes relevant to free will. Under reductionist determinism, moral responsibility is threatened, as agents cannot be held accountable for actions fully predetermined by prior physical states; however, compatibilist views maintain that responsibility persists through the predictable consequences of character and choices within a deterministic system.^[75]

Scientific and Emergentist Critiques

Emergentist critiques of reductionism argue that complex systems exhibit properties that arise unpredictably from the interactions of their components, rendering full explanation in terms of lower-level parts impossible. In his 1925 work The Mind and Its Place in Nature, philosopher C.D. Broad distinguished between "resultant" properties, which can be mechanistically predicted from parts (e.g., the weight of a table as the sum of its components), and "emergent" properties, which cannot be deduced even with complete knowledge of the parts and their interactions, such as novel chemical properties in compounds. Broad identified types of emergence, including qualitative novelty where higher-level phenomena introduce entirely new laws not reducible to those governing simpler entities. This framework challenges ontological reductionism by positing that wholes possess irreducible attributes, as seen in debates over consciousness emerging from neural activity without being fully explainable by individual neuron firings.^[76] In biology, emergentist perspectives highlight how ecosystem dynamics cannot be reduced to genetic or molecular levels alone, as interactions produce holistic behaviors. The Gaia hypothesis, proposed by James Lovelock in 1979, posits Earth as a self-regulating system where life maintains planetary conditions conducive to its persistence, with emergent feedbacks like atmospheric composition arising from biosphere-geosphere interactions rather than isolated components. For instance, oxygen levels are stabilized not by individual organisms but through global biogeochemical cycles that defy reduction to genetic determinism. This view underscores reductionism's inadequacy for holistic systems, where methodological approaches focusing on parts fail to capture system-wide regulation.^[77] Physics provides further empirical challenges through phenomena like chaos theory and quantum mechanics. Edward Lorenz's 1963 paper demonstrated that deterministic systems, such as atmospheric models, exhibit sensitive dependence on initial conditions, where minute variations lead to vastly different outcomes, making long-term predictions irreducible to precise micro-level computations. This "butterfly effect" illustrates how emergent unpredictability arises in non-linear dynamics, limiting reductionist explanations in complex physical systems. Similarly, quantum entanglement reveals non-local correlations, as formalized in John Bell's 1964 theorem, where measurements on separated particles instantaneously influence each other, violating local realism and showing that particle properties cannot be independently reduced without holistic quantum descriptions.^[78] Key arguments against reductionism emphasize scale-dependent laws and computational limits. Physicist Philip W. Anderson's 1972 essay "More Is Different" contends that while reductionism works at certain scales, emergent behaviors at higher levels introduce new principles, such as broken symmetry in condensed matter physics, where collective electron behaviors yield superconductivity not predictable from quantum mechanics alone. Anderson argued that complexity hierarchies prevent full upward reduction, as "the ability to reduce everything to simple fundamental laws does not imply the ability to start from those laws and reconstruct the universe." In computational simulations, this manifests as irreducible emergence; for example, attempts to model complex systems like weather or brains encounter limits where interactions produce outcomes beyond exhaustive part-by-part calculation due to exponential complexity.^[79] A specific illustration is the failure of full reduction in climate modeling, where emergent weather patterns arise from chaotic atmospheric interactions that cannot be perfectly simulated from molecular dynamics. Despite advances in resolving finer scales, models like those from the IPCC rely on parameterizations for unresolved processes, as complete reduction to atomic levels is computationally infeasible and yields unpredictable macro-patterns due to non-linearity, highlighting emergence's role in persistent uncertainties.^[80]

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Metaphysical reduction: This refers to theses like metaphysical reductionism or ... whether it should be categorized as explanatory reduction is unclear (see ...
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Ancient Atomism - Stanford Encyclopedia of Philosophy
Oct 18, 2022 · Democritus is reported to have given an account of the origin of human beings from the earth. He is also said to be the founder of a kind of ...
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Descartes' Physics - Stanford Encyclopedia of Philosophy
Jul 29, 2005 · Nevertheless, even if Descartes' mechanistic natural philosophy ... reductionism (i.e., that material bodies are simply extension and its modes).A Brief History of Descartes... · The Laws of Motion and the...
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Reductionism in Biology - Stanford Encyclopedia of Philosophy
May 27, 2008 · Reductionism encompasses a set of ontological, epistemological, and methodological claims about the relations between different scientific domains.Introduction · Problems with Reductionism · “Alternatives” to Reductionism...
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Vienna Circle - Stanford Encyclopedia of Philosophy
Jun 28, 2006 · The Vienna Circle was a group of early twentieth-century philosophers who sought to reconceptualize empiricism by means of their interpretation of then recent ...
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Systems biology, emergence and antireductionism - ScienceDirect
Ontological reductionism stated that physical–chemical entities and processes are essentially same for inanimate nature and living organisms. The difference ...
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[PDF] Quantum Field Theory and the Limits of Reductionism
Jul 30, 2024 · It is true that if ontological reductionism is false in QFT it is likely that methodological reductionism will not be a good strategy for making ...
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Supervenience and Mind - Cambridge University Press
Jaegwon Kim is one of the most pre-eminent and most influential contributors to the philosophy of mind and metaphysics. This collection of essays presents ...
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[PDF] To defend mereological reductionism from 2 objections - S-Space
In this paper, I will deal with what mereological reductionism is, what problem occurs if we accept mereological reductionism and.
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On Mereology and Metricality | Philosophers' Imprint
Feb 12, 2024 · This article motivates and develops a reductive account of the structure of certain physical quantities in terms of their mereology.
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[PDF] Reductionism and its heuristics: Making methodological ...
Abstract Methodological reductionists practice 'wannabe reductionism'. They claim that one should pursue reductionism, but never propose how.Missing: Enlightenment | Show results with:Enlightenment
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Reduction and Emergence in Chemistry
The aim of this article is to present a different perspective through which to examine reduction and emergence; namely, the perspective of chemistry's relation ...
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[PDF] Unity of science as a working hypothesis
Unity of Science is the aim of this paper, referring to an ideal state of science and a trend within science, with three broad concepts.
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The Unity of Science - Stanford Encyclopedia of Philosophy
Aug 9, 2007 · Reductionism is the adoption of reduction relations as the global ideal or standard of a proper unified structure of scientific knowledge; and ...1. Historical Development In... · 3. Epistemological Unities · 3.3 Epistemic Roles: From...
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Karl Popper - Stanford Encyclopedia of Philosophy
Nov 13, 1997 · The logic of his theory is utterly simple: a universal statement is falsified by a single genuine counter-instance. Methodologically, however, ...
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The limits of falsifiability: Dimensionality, measurement thresholds ...
Oct 11, 2025 · Karl Popper's falsifiability criterion assumes that scientific hypotheses can be reduced to binary tests. We show this assumption is ...<|control11|><|separator|>
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[PDF] the structure of science - HIST-Analytic
Apr 23, 2015 · Erngst Nagel ..LUMBTA uNrvERsrrY. THE STRUCTURE. OF SCIENCE ?roblems ... 346 The Structure of Science a. In the highly developed science ...
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Derivation of Kinetic Theory of Gas Molecules - BYJU'S
The kinetic theory of gases relates the macroscopic property of the gas, like – Temperature, Pressure, and Volume to the microscopic property of the gas, ...
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ON THE REDUCTION OF GENETICS TO MOLECULAR BIOLOGY
Instead, it is argued that genetics has been partially reduced to molecular biology in the sense of token-token reduction. I. According to one received view of ...
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The Multiple Realizability Argument Against Reductionism
Aug 5, 2025 · These claims are widely supposed to have been refuted by the multiple realizability argument, formulated by Putnam (1967, 1975) and Fodor (1968 ...
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Reduction as an a posteriori Relation
So, for example, the reduction of classical to quantum mechanics requires that every classical system be more accurately and precisely regarded as a quantum ...2 Reduction As Domain... · 3 A Formal Approach To... · 4 An Empirical Approach To...
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The Relation Between Classical and Quantum Mechanics - ADS
... mechanics are weakly equivalent over a domain of applicability, and concludes that, in this restricted sense, classical mechanics reduces to quantum mechanics.
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Unification in Physics - Oxford Academic
In many cases of unification not only is there an ontological reduction where different phenomena, usually forces, are seen as one and the same, but the ...
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Chemical reductionism revisited: Lewis, Pauling and the physico ...
In the molecular orbital theory, which was developed originally in the work of chemical physicist Robert Mulliken and physicist Friedrich Hund in the late 1920 ...
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Reduction and Emergence in Chemistry—Two Recent Approaches
Two articles on the reduction of chemistry are examined. The first, by McLaughlin. (1992), claims that chemistry is reduced to physics and that there is no ...
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[PDF] A Structure for Deoxyribose Nucleic Acid
This structure has novel features which are of considerable biological interest. A structure for nucleic acid has already been proposed by Pauling and Corey'.
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Neurobiological reduction: From cellular explanations of behavior to ...
Dec 22, 2022 · The reductionist belief that molecular and cellular properties underlie cognition and behavior has been called the neuron doctrine (e.g., Barlow ...
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The Watson-Crick Model and Reductionism - SpringerLink
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A Perspective on Protein Structure Prediction Using Quantum ...
We share our perspective on how to create a framework for systematically selecting protein structure prediction problems that are amenable for quantum ...Introduction · What Makes Protein Structure... · A Quantum-Classical Hybrid...Missing: reductionism | Show results with:reductionism
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The Higgs boson - CERN
The existence of this mass-giving field was confirmed in 2012, when the Higgs boson particle was discovered at CERN.Missing: reductionism | Show results with:reductionism
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Full microscopic simulations uncover persistent quantum effects in ...
Oct 1, 2025 · The presence of quantum effects in photosynthetic excitation energy transfer has been intensely debated over the past decade.
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Explaining the Efficiency of Photosynthesis: Quantum Uncertainty or ...
Apr 11, 2022 · In particular, it has been proposed that the vibrations that mediate the flow of energy between pigments exhibit nontrivial quantum effects, ...Methods · Supporting Information · Author Information · References
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Zermelo, Reductionism, and the Philosophy of Mathematics
In his [9], Hubert completes this task for Euclidean geometry. During the same period, he offers a set of axioms for the real number system in Hubert [10] ...
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Set Theory - Stanford Encyclopedia of Philosophy
Oct 8, 2014 · Set theory is the mathematical theory of well-determined collections, called sets, of objects that are called members, or elements, of the set.Missing: reductionism | Show results with:reductionism
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E.W.Dijkstra Archive: Notes on Structured Programming (EWD 249)
There is a second source of inspiration to be found in our experience. In the process of step-wise program composition, proceeding from outside inwards, going ...Missing: modular | Show results with:modular
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[PDF] Reflections on Classical and Nonclassical Modularity
It is not surprising that this idea has been picked up and advocated in programming once program size became an issue [16, 59]. Reductionism is an implicit ...
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Computational Complexity Theory
Jul 27, 2015 · Computational complexity theory is a subfield of theoretical computer science one of whose primary goals is to classify and compare the practical difficulty of ...
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[PDF] The Complexity of Theorem-Proving Procedures - Computer Science
A method of measuring the complexity of proof procedures for the predicate calculus is introduced and discussed. Throughout this paper, a set of strings means a ...
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[PDF] ON COMPUTABLE NUMBERS, WITH AN APPLICATION TO THE ...
A number is computable if it differs by an integer from the number computed by a circle-free machine. We shall avoid confusion by speaking more often of ...
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[PDF] Divide-and-conquer algorithms - People @EECS
It was therefore a source of great excitement when in. 1969, the German mathematician Volker Strassen announced a significantly more efficient algorithm, based ...Missing: reductionism | Show results with:reductionism
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Gödel's incompleteness theorems
Nov 11, 2013 · Gödel's two incompleteness theorems are among the most important results in modern logic, and have deep implications for various issues.
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IS CONSCIOUSNESS A BRAIN PROCESS? - PLACE - 1956
IS CONSCIOUSNESS A BRAIN PROCESS? U. T. PLACE,. U. T. PLACE. Institute of ... First published: February 1956. https://doi.org/10.1111/j.2044-8295.1956 ...Missing: original details
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The Mind/Brain Identity Theory - Stanford Encyclopedia of Philosophy
Jan 12, 2000 · The notion 'type' and 'token' here comes by analogy from 'type' and 'token' as applied to words. A telegram 'love and love and love' contains ...Causal Role Theories · Type and Token Identity... · Later Objections to the Identity...<|separator|>
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Ethical Naturalism | The Oxford Handbook of Ethical Theory
This article defends naturalistic moral realism. It holds that the moral properties are ordinary properties such as the property of being a quarter dollar.
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Reduction and religion: Lessons from eliminative materialism - jstor
Religious experience cannot be reduced to brain states. Clearly, the conclusions drawn from these thought experiments are direcdy opposed to elimmative ...Missing: sources | Show results with:sources<|separator|>
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[PDF] Faith and Reason:The Synthesis of St.Thomas Aquinas
60 In the elaboration of theology reason does not provide strict demon- strations of the object of faith; but only presents some probable arguments. In the ...Missing: reductionism | Show results with:reductionism
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20th WCP: Anne Conway's Critique of Cartesian Dualism
Secondly, she argues that dualism results in mechanism because it makes too sharp a distinction between body and soul, thus regarding the body as a mechanical ...
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[PDF] The Influence and Legacy of Deism in Eighteenth Century America
Deism, a philosophy which had existed since ancient times, endorsed a reason based system that looked to the natural world for answers about God, life, and.
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Downward Causation - The Information Philosopher
Downward causation is a kind of holism that denies reductionism. "Wholes" can enforce constraints on their "parts" to make them move in ways that may be ...
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Philosophical and Scientific Perspectives on Downward Causation
Aug 1, 2017 · One way out of this dilemma is simply to give up on an ontologically robust sense of top-down causation. Some of this book's authors are happy ...
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THE METAPHYSICS OF DOWNWARD CAUSATION
Jun 1, 2013 · What we face today is a new opening for arguments challenging not only methodological, but also ontological and causal reductionism. However, ...
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Philosophical Foundations of Neuroscience | Reviews
$$39.95Sep 10, 2003 · To attribute such capacities to brains is to commit what Bennett and Hacker identify as “the mereological fallacy”, that is, the fallacy of ...
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Behind the Mereological Fallacy - jstor
sympathise with an injured hand rather than with the person whose hand it is. Bennett and Hacker formulate the relevant mereological fallacy as follows ...
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Supervenience - Stanford Encyclopedia of Philosophy
Jul 25, 2005 · The more interesting issue is whether supervenience suffices for reduction (see Kim 1984, 1990). This depends upon what reduction is taken to ...History · Supervenience and Other... · Varieties of Supervenience · Applications
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[PDF] The “Supervenience Argument”: Kim's Challenge to Nonreductive ...
ABSTRACT. Jaegwon Kim's “supervenience argument” purports to show that epiphenomenalism about the mental follows from premises that any nonreductive.
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Multiple Realizability - Stanford Encyclopedia of Philosophy
May 18, 2020 · The multiple realizability thesis contends that a single mental kind (property, state, event) can be realized by many distinct physical kinds.The Multiple Realizability... · Replies to Multiple... · The Shifting Status of Multiple...
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The Multiple Realizability Argument Against Reductionism
Apr 1, 2022 · The present paper criticizes the argument and identifies a reductionistic thesis that follows from one of the argument's premises. Information.
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Chaos - Stanford Encyclopedia of Philosophy
Jul 16, 2008 · The big news about chaos is supposed to be that the smallest of changes in a system can result in very large differences in that system's behavior.
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[PDF] The Limits of Reductionism - arXiv
Reductionism's limits arise from ignoring interactions, which are relevant in complex phenomena. Emergent properties cannot be reduced to lower scales.
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Introduction and Responses to Criticism of Irreducible Complexity
Feb 20, 2006 · In Darwin's Black Box (1996), Lehigh University biochemist Michael Behe proposed that many of these molecular machines exhibit irreducible complexity.
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[PDF] How to Rebut the Anti-reductionist Argument from Infinite Limits
Oct 6, 2017 · In Section 5, we respond to the anti-reductionist challenge on the basis of the results of Section 4: we argue that the explanatory appeal to ...
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Volition and the Brain – Revisiting a Classic Experimental Study - PMC
The 1983 study by Libet et al. [1] investigated the brain processes underlying the awareness of intending and initiating voluntary, endogenous actions.
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Elbow Room: The Varieties of Free Will Worth Wanting
A landmark book in the debate over free will that makes the case for compatibilism.In this landmark 1984 work on free will, Daniel Dennett makes a case for.
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[PDF] Kim on Causation and Mental Causation - PhilArchive
Abstract: Jaegwon Kim's views on mental causation and the exclusion argument are evaluated systematically. Particular attention is paid to different theories ...
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[PDF] Causal Exclusion without Causal Sufficiency - PhilArchive
Mental Causation and Non-Reductionism together entail that physical phenomena are systematically caused by phenomena that are distinct from physical phenom- ...
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[PDF] epiphenomenalism.pdf - Nicholas J.J. Smith
Epiphenomenalism states that only physical states have causal power, and mental states are dependent on them, playing no causal role.
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Kim on Mental Causation and Causal Exclusion - jstor
For three decades Jaegwon Kim has articulated and defended the view that mental properties are distinct from physical properties, are supervenient on phys-.
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For Whom Does Determinism Undermine Moral Responsibility ... - NIH
Philosophers have long debated whether, if determinism is true, we should hold people morally responsible for their actions since in a deterministic universe, ...
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Mind and its place in nature - Internet Archive
... MIND AND ITS PLACE IN NATURE. I quite explicitly confined himself to the study of Nature. I as an object of Mind. He refused to complicate his problem by ...
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Gaia - James Lovelock - Oxford University Press
$$22.99James Lovelock is the originator of the Gaia Hypothesis (now Gaia Theory). His books include Gaia: a new look at life on Earth (OUP, 1979); The Ages of Gaia (WW ...Missing: paper | Show results with:paper<|control11|><|separator|>
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Deterministic Nonperiodic Flow in - AMS Journals
Deterministic Nonperiodic Flow. Edward N. Lorenz. Edward N. Lorenz Massachusetts Institute of Technology Search for other papers by Edward N. Lorenz in
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More Is Different - Science
More Is Different: Broken symmetry and the nature of the hierarchical structure of science. P. W. AndersonAuthors Info & Affiliations. Science. 4 Aug ...
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Predicting Climate Change: Lessons From Reductionism ...
Jun 3, 2011 · This Forum highlights the concepts of reductionism and emergence, and past climate variability, to illuminate some of the uncertainties faced ...Missing: critiques | Show results with:critiques