Fact-checked by Grok 2 weeks ago

Ab initio

Ab initio is a Latin phrase meaning "from the beginning" or "from first principles".[] It is used across various fields to denote approaches or analyses that start from fundamental principles without relying on prior assumptions or empirical data derived from observation. In , ab initio refers to something that is valid or void from the outset, such as a that is null from its . In and , it describes reasoning or derivations built from basic axioms. The phrase also appears in other contexts, including and computing. In scientific and engineering applications, particularly and , ab initio methods predict properties of atoms, molecules, and materials directly from first principles, relying on fundamental physical laws such as the without empirical parameters. These methods solve the electronic to determine electronic energies, wavefunctions, and derived properties like molecular geometries and reaction pathways, typically for systems up to 100–1000 atoms. Key approaches include Hartree–Fock (), post-HF methods like Møller-Plesset () and coupled cluster theory (CCSD(T)), and (DFT), which is often included despite approximate functionals. The development of these scientific methods spans over five decades since early implementations in the , with foundational contributions recognized by the 1998 to and . Advances in computing have enabled broader applications, such as in and , though limitations in scalability and approximations persist. Detailed discussions of , legal, philosophical, and other uses follow in subsequent sections.

Etymology and Definition

Phrase Origin

The Latin phrase ab initio is derived from the preposition ab, meaning "from" or "away from," combined with initio, the ablative singular form of initium, which signifies "beginning," "entrance," or "start," thus forming a prepositional phrase that literally conveys origin at the source. In classical Latin literature, ab initio appears in texts from the 1st century BCE, notably in the works of , such as his and Pro Cluentio, where it is employed to indicate actions or conditions originating from the very outset. The phrase persisted through Medieval Latin, used in ecclesiastical, legal, and scholarly writings as Latin remained the lingua franca of European intellectual traditions, before its integration into English vernacular contexts by the early 17th century, with documented appearances in legal and academic prose around 1600. In modern English usage, ab initio is typically pronounced /ˌæb ɪˈnɪʃ.i.oʊ/, reflecting anglicized ecclesiastical influences, though academic and classical philology settings may favor a pronunciation closer to the original Latin, such as /ab ɪˈniː.ti.oː/.

Meaning and Translation

The Latin phrase ab initio translates to "from the beginning" in English, denoting an approach or state originating at the foundational level without dependence on prior developments or assumptions. This rendering emphasizes a derived directly from initial principles, often implying a complete restart or inherent validity (or invalidity) from the outset. A key nuance of ab initio lies in its contrast with ex post facto, which means "after the fact" and refers to retrospective application or , whereas ab initio stresses prospective or intrinsic origins without intermediary reliance. In contexts like formal , it underscores derivations built solely on basic axioms, avoiding empirical shortcuts or post-hoc adjustments. In other languages, the phrase is frequently retained in its Latin form, particularly in legal, scientific, and academic , but equivalents capture its core sense. In , it corresponds to dès le début or dès l'origine, meaning "from the beginning" or "from the outset." uses von Anfang an or von vornherein, translating to "from the beginning" or "from the outset." In , the Real Academia Española defines it as desde el principio, with synonyms like ab ovo or ab origine, both signifying "from the beginning." In English, ab initio functions idiomatically as an in formal writing to indicate foundational or , as in "The was developed ab initio to ensure logical ." It also appears adjectivally, describing methods "based on first principles," such as in computational models predicted ab initio.

Contract Law

In law, ab initio refers to the principle that certain agreements are void from their very , meaning they lack any legal validity or enforceability as if they had never been formed. This occurs when a contract is inherently flawed due to illegality, such as agreements to perform unlawful acts like crimes or violations of ; lack of capacity, including contracts entered by minors or mentally incompetent individuals; or initial impossibility of performance, where the subject matter cannot legally or factually be fulfilled at formation. Under this doctrine, no rights or obligations arise under the contract, distinguishing it sharply from voidable contracts, which remain valid and enforceable until affirmatively disaffirmed by the aggrieved , such as in cases of , duress, or mutual mistake. The concept is deeply rooted in English , where courts have long held that contracts contravening or fundamental legal prohibitions produce no legal consequences. A seminal is Cope v. Rowlands (1836), in which Baron Parke ruled that a broker's unlicensed agreement for stock transactions, prohibited by , was utterly void and could not support any claim for or services, emphasizing that "where the contract which the plaintiff seeks to enforce... is expressly... forbidden by the , or... the interest... be in violation of the policy of the law," it must be deemed a nullity. This principle underscores the policy of deterring illegal or inequitable dealings by denying courts the power to validate them retrospectively. In modern U.S. law, the § 2-302 codifies protections against , allowing courts to refuse enforcement of contracts or clauses found unconscionable at formation, effectively treating them as void ab initio to prevent oppression or unfair surprise; for instance, in Williams v. Walker-Thomas Furniture Co. (1965), the D.C. Circuit invalidated a cross-collateralization clause in a consumer credit sale due to procedural and substantive . Similarly, in the , Council Directive 93/13/EEC on unfair terms in consumer contracts declares such terms non-binding on the consumer, and where the contract cannot subsist without the unfair provision, courts in member states may declare the entire agreement void from the outset, as affirmed in CJEU jurisprudence emphasizing without time limits for nullity claims. Remedies for void ab initio contracts focus on restitution rather than enforcement or damages, aiming to restore parties to their pre-contract positions by requiring return of any benefits conferred to avoid unjust enrichment. The Restatement (Second) of Contracts § 197 provides that relief, including restitution, is available for partially performed void contracts unless denial would produce a disproportionate forfeiture, but ratification is impossible since the agreement never held legal force. This equitable approach ensures fairness without retroactively validating the invalid deal. In , the principle of ab initio invalidity applies to laws or governmental actions that violate or constitutional provisions from the moment of their enactment, rendering them void as if they never existed. This doctrine was foundationalized in the U.S. case Marbury v. Madison (1803), where Chief Justice declared that any legislative act repugnant to the Constitution is void and has no legal effect, establishing as a mechanism to nullify such unconstitutional measures retroactively. Courts in various jurisdictions have since applied this to strike down statutes or executive actions that infringe on core , ensuring that unconstitutional elements do not bind legal proceedings or citizens from inception. In , ab initio nullity arises when fundamental errors, such as lack of , render judicial or administrative proceedings entirely void from the start, necessitating dismissal without regard to subsequent actions. A seminal example is the UK House of Lords decision in Anisminic Ltd v. Foreign Compensation Commission 2 AC 147, where the court held that an administrative decision made without due to an error of was a nullity ab initio, incapable of producing legal effects and subject to full despite ouster clauses attempting to limit challenges. This approach underscores that jurisdictional defects taint the entire process retroactively, distinguishing it from mere irregularities that might allow partial validation. In , treaties conflicting with peremptory norms (jus cogens)—such as prohibitions against or —are void ab initio under Article 53 of the on the Law of Treaties (1969), meaning they lack all legal validity from the time of conclusion and cannot be invoked to justify any obligations. Article 71 further mandates that parties eliminate the consequences of acts performed under such treaties to the extent possible, reinforcing the retroactive nullity to prevent perpetuation of violations against foundational international principles. This provision codifies , ensuring that no derogation from jus cogens is tolerated, even in agreements otherwise duly executed. Developments in data privacy law illustrate ab initio invalidity in the context of , particularly under the EU's (GDPR). In the Court of Justice of the (CJEU) ruling in Data Protection Commissioner v. Facebook Ireland Ltd. (Schrems II, 2020), the Privacy Shield framework for EU-US data transfers was declared invalid from its due to inadequate safeguards against unlawful , rendering prior transfers under it non-compliant and requiring immediate cessation and remediation of affected . Following this, the EU-US Data Privacy Framework was adopted in July 2023 as a replacement, though it faces ongoing legal challenges (e.g., Schrems III). Additionally, as of 2025, enforcement actions such as the €1.2 billion fine against in 2023 for unlawful data transfers post-Schrems II underscore the retroactive invalidity of non-compliant processing, obligating and penalties. For instance, the CJEU's 2023 ruling in Case C-300/21 addressed the validity of in online platforms, reinforcing that invalid consents render processing unlawful from the outset. The (EDPB) Opinion 08/2024 further clarified that "consent or pay" models often fail to obtain valid , leading to ab initio invalid . The distinction between ab initio nullity and ex nunc invalidity is critical: the former operates retroactively, erasing all effects from the outset as if the act never happened, whereas the latter applies prospectively from the point of declaration, preserving prior consequences while voiding future ones. This contrast ensures that severe foundational flaws, unlike remediable defects, trigger comprehensive unwinding to uphold legal integrity.

Scientific and Engineering Applications

Computational Chemistry

In , ab initio methods refer to first-principles approaches that solve the time-independent to determine the electronic structure and properties of molecules, relying solely on fundamental physical constants and quantum mechanical principles without empirical parameters. The central equation is \hat{H} \Psi = E \Psi, where \hat{H} is the , \Psi is the total wavefunction, and E is the energy eigenvalue; this equation is solved variationally or perturbatively for the ground and excited states of molecular systems. These methods provide theoretically rigorous predictions of molecular behavior, enabling the computation of energies, geometries, and spectra from atomic composition alone. A foundational ab initio technique is Hartree-Fock (HF) theory, which approximates the many-electron wavefunction as a single Slater determinant of one-electron molecular orbitals, effectively treating electron-electron interactions through a mean-field approach. The HF energy expression is given by E_{\mathrm{HF}} = \sum_i \langle i | h | i \rangle + \frac{1}{2} \sum_{ij} \left( \langle ij || ij \rangle - \langle ij || ji \rangle \right), where h is the one-electron core Hamiltonian, the first sum represents kinetic and nuclear attraction energies, and the double sum accounts for Coulomb and exchange interactions between occupied orbitals i and j. This self-consistent field method, formalized for molecular systems in Roothaan's seminal 1951 work on \pi-electron systems, marked the first practical ab initio calculation in quantum chemistry. To account for electron correlation neglected in , post-HF methods such as second-order Møller-Plesset (MP2) are employed, treating correlation as a perturbation on the HF reference and improving accuracy for weakly correlated systems. Ab initio calculations find widespread applications in predicting molecular geometries, reaction energies, and vibrational spectra; for instance, HF theory with a near-complete basis yields an O-H of 0.941 in , slightly shorter than the experimental value of 0.957 , highlighting the method's utility despite correlation effects. Despite their precision, ab initio methods suffer from high computational cost, with HF scaling as O(N^4) where N is the number of basis functions, limiting routine use to small- to medium-sized molecules. This challenge is mitigated by judicious choice of basis sets, such as Dunning's correlation-consistent polarized valence double-zeta (cc-pVDZ) set, which balances accuracy and efficiency by systematically converging toward the complete basis set limit.

Physics and Materials Science

In physics and materials science, ab initio methods involve computational simulations of material properties derived solely from fundamental laws of quantum mechanics, without empirical parameters or experimental fitting. These techniques solve the many-electron Schrödinger equation or its approximations to predict electronic, structural, and dynamic behaviors in solids and extended systems. Density functional theory (DFT) serves as a widely used semi-ab initio approach, mapping the complex many-body problem onto an effective single-particle framework via the electron density, though it relies on approximate exchange-correlation functionals that can introduce errors in excited-state properties. For more rigorous treatments, pure ab initio methods such as many-body perturbation theory (MBPT) incorporate electron-electron interactions beyond mean-field levels, enabling accurate descriptions of quasiparticle states and response functions in periodic materials. A prominent example within MBPT is the , which computes the operator as \Sigma = iGW, where G represents the non-interacting and W the dynamically screened interaction. This approach excels in determining band structures, particularly correcting the systematic underestimation of s in semiconductors by semilocal DFT functionals. For instance, in , standard DFT () predicts an indirect of about 0.6 eV, while GW refinements yield values around 1.17 eV, aligning closely with the experimental indirect gap of 1.12 eV and enabling reliable predictions of optical absorption edges. Similarly, ab initio calculations assess defect formation energies in two-dimensional materials like , where monovacancies exhibit energies of approximately 7.5–8.0 eV, influencing scattering and thermal conductivity. In contexts, ab initio methods facilitate the design of alloys and by providing parameter-free insights into stability and functionality. Ab initio (AIMD), which couples DFT with classical dynamics, simulates finite-temperature processes such as phase transitions; for example, in TiO₂, AIMD reveals the pressure-induced shift from the to the phase above 10 GPa, driven by octahedral distortions and relevant for high-pressure synthesis of ceramics. Post-2010 advancements have leveraged to accelerate these computations, with neural networks trained on ab initio datasets surrogate-modeling potentials for systems beyond direct reach, achieving near-DFT accuracy at reduced cost. Plane-wave basis sets, prevalent in solid-state implementations, enhance for compared to molecular chemistry's localized orbitals, as implemented in software like , which employs projector-augmented waves for efficient total-energy evaluations. Unlike empirical potentials, which parameterize interatomic forces from experimental data for large-scale simulations of defects or fractures, ab initio methods ensure predictions grounded in quantum principles, avoiding transferability issues across compositions but at the expense of high computational demand—typically limiting routine applications to 100–1000 atoms. This trade-off underscores their role in validating empirical models and exploring novel materials where data is scarce.

Philosophical and Broader Uses

Philosophy and Logic

In philosophy, reasoning ab initio refers to the construction of arguments from first principles or fundamental , eschewing unexamined assumptions or empirical contingencies to establish a secure foundational basis for . This approach emphasizes deriving conclusions deductively from self-evident primitives, ensuring that the entire edifice of reasoning is transparent and justifiable at every step. A seminal example is ' method in his (1641), where he employs methodical doubt to strip away all preconceptions and rebuild certainty starting from the indubitable cogito (", therefore ") as the primary . In formal logic, ab initio deduction manifests in axiomatic systems that begin with a minimal set of undefined terms and postulates, from which theorems are rigorously derived. exemplifies this, as outlined in Euclid's Elements (c. 300 BCE), where five postulates and common notions serve as the starting point for proving all subsequent geometric truths through logical inference alone, without reliance on measurement or observation. This method underscores the ideal of logical purity, where validity stems solely from the of the axioms rather than external validation. Historically, the concept traces back to Aristotle's (c. 350 BCE), which describes scientific (apodeixis) as proceeding ab initio from primitive principles that are true, primary, and better known than their consequents, forming the basis for syllogistic reasoning in demonstrative sciences. further developed this in his (1781), invoking ab initio synthetic a priori judgments— that is universal and necessary yet extends beyond analytic tautologies—derived from the innate structures of human , such as and time as forms of . In modern , ab initio arguments appear in ethical theory, notably ' "" in (1971), a hypothetical that constructs principles of justice from a veil of ignorance, abstracting from contingent social facts to foundational . This contrasts sharply with , which builds generalizations bottom-up from observed particulars; ab initio methods are top-down and foundational, prioritizing the axiomatic origins of justification over empirical accumulation, as highlighted in discussions of rationalist epistemologies. Critics of ab initio reasoning, however, point to the risk of circularity if the chosen axioms are not truly primitive but implicitly presuppose the conclusions they support, a concern raised in foundational debates like those surrounding the status of parallels in non-Euclidean geometries or , which reveal limits to fully self-contained deductive systems.

Miscellaneous Applications

In business and finance, the term "ab initio" refers to pricing models for financial that are derived directly from economic principles, such as risk-neutral valuation, without relying on empirical data or historical calibrations. For instance, the Black-Scholes model, while incorporating some market assumptions, exemplifies a semi-ab initio approach by solving the governing option prices from first principles under idealized conditions like continuous trading and no . More purely ab initio methods appear in modern contexts, such as out-of-sample pricing of volatility index options using generalized autoregressive conditional heteroskedasticity (GARCH) models, where parameters are estimated solely from current to generate valuations. In computing and , "ab initio" describes program design and development starting from core algorithms and basic machine instructions, eschewing pre-existing libraries or higher-level tools to ensure foundational control and optimization. This approach was essential in the during early compiler development, when pioneers like created the first compilers—such as the A-0 system for the in 1952—by manually coding translation routines in or , laying the groundwork for high-level programming languages like . In contemporary , ab initio techniques manifest in the synthesis of algorithms or circuits from primitive components, as seen in efforts to generate quantum circuits via energy minimization without template reliance, enabling novel explorations in computational efficiency. In education, ab initio curricula are structured to build knowledge from zero prior assumptions, fostering foundational skills through self-directed exploration, as exemplified by Montessori methods that emphasize hands-on, child-led learning starting from innate curiosities rather than rote memorization. This principle is prominently applied in International Baccalaureate (IB) programs offered at Montessori schools, where "ab initio" language courses—such as or —teach beginners from the ground up over two years, integrating cultural contexts to develop without prerequisites. Such designs promote equity by accommodating diverse learner backgrounds and aligning with broader pedagogical shifts toward inclusive, principle-based instruction. Post-2020 applications in leverage ab initio life-cycle assessments (LCAs) for emerging eco-materials, computing environmental impacts from basic physical and chemical principles when historical data is unavailable, thus enabling proactive design of low-carbon alternatives like advanced biofuels or recycled composites. For example, optimizations for microbial production pathways integrate ab initio metrics—drawing from ISO 14040 frameworks—to evaluate cradle-to-grave effects without proxy assumptions, revealing trade-offs in energy use and emissions for scalable green technologies. This approach supports and in circular economies by quantifying uncertainties in novel processes. Culturally, "ab initio" appears in literature as a motif for origin narratives, particularly in science fiction exploring creation and consequences from foundational beginnings. A notable example is the 2025 novel ab initio by Jacob Terracina, which weaves nonlinear storytelling around the emergence of advanced artificial intelligence, probing ethical dilemmas in its inception through the lens of a biologist-engineer protagonist. Such works use the phrase to evoke themes of purity in genesis, bridging technical concepts with speculative inquiries into human-AI coexistence.

References

  1. [1]
    Ab Initio Method - an overview | ScienceDirect Topics
    Ab initio methods refer to computational techniques that are based solely on fundamental physical laws and postulates, without relying on experimental ...
  2. [2]
    Ab initio quantum chemistry: Methodology and applications - PNAS
    May 10, 2005 · This Perspective provides an overview of state-of-the-art ab initio quantum chemical methodology and applications.
  3. [3]
    None
    Nothing is retrieved...<|control11|><|separator|>
  4. [4]
    AB INITIO definition and meaning | Collins English Dictionary
    ab initio in British English. Latin (æb ɪˈnɪʃɪˌəʊ IPA Pronunciation Guide ).
  5. [5]
    What does "ab initio" mean in Latin? - WordHippo
    More meanings for ab initio. from the beginning adverb. ab initio · at first adverb. primo, primum, initio, primitus, ab incepto · from the start · ab initio.
  6. [6]
    None
    ### Summary of Void Contracts Ab Initio and Voidable Contracts in Contract Law
  7. [7]
    [PDF] Report on Relief Under Legally Defective Contracts
    249 the effect of illegality is described in some portions of the judgments as rendering a contract unenforceable and in others as making it “void ab initio.”.
  8. [8]
    2-302. Unconscionable contract or Clause. - Law.Cornell.Edu
    An unconscionable contract may be refused, enforced without the clause, or the clause limited. Parties can present evidence of commercial setting, purpose and ...Missing: ab initio
  9. [9]
  10. [10]
    Marbury v. Madison | 5 U.S. 137 (1803)
    If an act of the Legislature repugnant to the Constitution is void, does it, notwithstanding its invalidity, bind the Courts and oblige them to give it effect?
  11. [11]
    Anisminic Ltd. v. Foreign Compensation Commission
    Some decisions are good while they stand; others are void ab initio. The decision of the commission is a complete nullity. If it is not a nullity the appellants ...
  12. [12]
    [PDF] Vienna Convention on the Law of Treaties (1969)
    Jan 27, 1980 · In the case of a treaty which is void under article 53 the parties shall: (a) eliminate as far as possible the consequences of any act ...
  13. [13]
    A mathematical and computational review of Hartree-Fock SCF ...
    May 2, 2007 · We present here a review of the fundamental topics of Hartree-Fock theory in Quantum Chemistry. From the molecular Hamiltonian, using and discussing the Born- ...
  14. [14]
    New Developments in Molecular Orbital Theory | Rev. Mod. Phys.
    New Developments in Molecular Orbital Theory. C. C. J. Roothaan · C. C. J. Roothaan. Department of Physics, University of Chicago, Chicago, Illinois. PDF Share.
  15. [15]
    Note on an Approximation Treatment for Many-Electron Systems
    A perturbation theory is developed for treating a system of n electrons in which the Hartree-Fock solution appears as the zero-order approximation.
  16. [16]
    Near Hartree‐Fock Calculations on the Ground State of the Water ...
    The calculated bond length, 0.941 Å, and bond angle 106.6°, are in good agreement with the experimental values, 0.957 Å and 104.52°. In spite of the rather ...
  17. [17]
    [PDF] An Introduction to Density Functional Theory
    For the past 30 years density functional theory has been the dominant method for the quantum mechanical simulation of periodic systems.
  18. [18]
    The mechanism of high pressure-induced phase transition in ...
    ... ab initio molecular dynamics (AIMD) simulations. Under high pressure, TiO2 undergoes a structural phase transition from the anatase phase to the baddeleyite ...
  19. [19]
    Ab Initio Machine Learning in Chemical Compound Space
    Aug 13, 2021 · We review studies aimed at tackling this challenge using modern machine learning techniques based on (i) synthetic data, typically generated using quantum ...<|control11|><|separator|>
  20. [20]
    (PDF) Ab Initio Computational Materials Science - ResearchGate
    Jan 17, 2025 · We present an overview of the capabilities of ab initio methods in the structural and mechanical properties, illustrated with an example for 2D ...
  21. [21]
    Modeling the structure of zircon (ZrSiO4): empirical potentials, ab ...
    Either empirical potentials or ab initio electronic structure methods may be used, depending on the physical phenomenon. Irradiation effects involving a very ...
  22. [22]
    [PDF] Analytical and Numerical Methods for Pricing Financial Derivatives
    ... ab initio, i.e., starting from the given initial value s without knowing the past history of the process. Assumption of a Markov character of asset prices ...
  23. [23]
    GARCH pricing and hedging of VIX options - Liu - Wiley Online Library
    Feb 24, 2022 · Our pricing is ab initio and out-of-sample and can be implemented in real time. Importantly, we propose the so-called single-option hedge error, ...
  24. [24]
    [PDF] History of Compilers - cs.wisc.edu
    One of the first real compilers was the FORTRAN compiler of the late. 1950s. It allowed a programmer to use a problem-oriented source language. Ambitious ...Missing: principles | Show results with:principles
  25. [25]
    Compiler Toolbox - School of Computing Science
    ... Compiler Design, by Aho and Ullman. Unless you are designing a programming language ab initio this is unlikely to be a problem you will encounter. 3.1 ...
  26. [26]
    Exploring ab initio machine synthesis of quantum circuits - IOPscience
    Jul 31, 2023 · Exploring ab initio machine synthesis of quantum circuits · 1. Introduction · 2. Unitary equivalence via energy minimisation · 3. Ab initio circuit ...
  27. [27]
    [PDF] The Montessori School Kingsley Inc. LANGUAGE POLICY
    Aug 11, 2022 · Students who wish to pursue language studies at Language B or Ab Initio level not offered by the School are provided the opportunity of ...
  28. [28]
    International Baccalaureate (IB) - Elonera Montessori School
    In Stage 6, Diploma Programme students study French ab initio, learning a new language from the ground up, fostering global perspectives and intercultural ...
  29. [29]
    Sustainable metabolic engineering for sustainability optimisation of ...
    Aug 25, 2021 · Thus, the necessary elements for ab initio sustainability assessment are ... Environmental management – Life cycle assessment – Principles and framework 2006.
  30. [30]
    Use of process simulation to obtain life cycle inventory data for LCA
    Sep 15, 2024 · Ab Initio methods are used for estimating missing data, literature ... Mineral processing simulation based-environmental life cycle assessment for ...
  31. [31]
    ab initio: a novel: 9798992540406: Terracina, Jacob ... - Amazon.com
    ab initio · a novel ; Quantity:1 ; Shipped & Sold by. Amazon.com ; Returns. FREE 30-day refund/replacement ; Payment. Secure transaction.