per accidens

1. Introduction

The term per accidens is a technical expression in Aristotelian and scholastic philosophy used to mark what holds only incidentally, non‑essentially, or by way of a conjunction rather than by nature. It is typically defined by contrast with per se (“through itself,” essentially). Where per se denotes what follows from a thing’s essence or proper nature, per accidens characterizes relations, properties, causes, or unities that arise from contingent or non‑defining features.

Historically, the expression originates as a Latin rendering of Aristotle’s Greek κατὰ συμβεβηκός (kata symbebēkos), which he opposes to καθ᾽ αὑτό (kath’ hautó, per se). This contrast becomes a key organizing device across three major domains:

Within scholastic systems, per accidens is not restricted to rare or random events. It includes regular, law‑like occurrences when these do not proceed from the essence of the agents involved. Thus, a father’s generating a white son is per accidens relative to the causal power of generation, even if such color outcomes are statistically common.

Different thinkers articulate the contrast in different ways—sometimes emphasizing logical structure of propositions, sometimes modes of being, sometimes causal dependence. Later Neo‑scholastic and analytic Thomist authors inherit the vocabulary and often focus especially on accidentally ordered causal series, in which each cause can act independently once in existence, in contrast to essentially ordered (per se) series.

Because per accidens ranges over predication, being, and causality, and because it does not simply mean “by chance,” modern interpreters frequently retain the Latin phrase to avoid conflation with everyday notions of accident or error. Subsequent sections trace its linguistic origins, Greek background, classical formulation in Aristotle, and later scholastic elaborations across logic, metaphysics, and natural philosophy.

2. Etymology and Linguistic Origins

The Latin phrase per accidens is morphologically transparent yet philosophically specialized. It combines per (“through, by, according to”) with accidens, the present participle of accidere (“to happen, to occur, to befall”). Literally, it can be read as “by what happens” or “according to what happens,” aligning closely with the Greek philosophical source.

From Accidere to Accidens

In classical Latin, accidere commonly denotes events that “happen” to someone or something, often with connotations of unexpectedness. The participle accidens came to be used substantivally for an “accident”: a property or event that befalls a subject without belonging to its essence.

Calque of Greek Philosophical Vocabulary

Scholars generally agree that per accidens is a deliberate Latin calque of Aristotle’s κατὰ συμβεβηκός. Here:

• κατά is rendered by per (“according to, in respect of”).
• συμβεβηκός (perfect participle of symbainein, “to happen, to occur”) is rendered by accidens.

Boethius and later medieval translators use per accidens as the standard equivalent, which gradually acquires a stable technical sense opposing per se across logic and metaphysics.

Semantic Field and Related Terms

Per accidens belongs to a broader Latin semantic field:

Medieval scholastics refine these nuances, reserving per accidens primarily for the logical, ontological, and causal opposition to per se, while allowing terms like casus and fortuitus to carry stronger notions of chance or fortune.

3. Greek Background: κατὰ συμβεβηκός

The conceptual ancestor of per accidens is Aristotle’s expression κατὰ συμβεβηκός (kata symbebēkós), usually rendered “according to what is incidental” or “in an accidental way.” It is systematically opposed to καθ᾽ αὑτό (kath’ hautó, per se).

The Verb συμβαίνειν and the Noun συμβεβηκός

Aristotle builds on ordinary Greek usage of συμβαίνειν (“to happen, to come about”) but gives the derived noun συμβεβηκός a technical sense:

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“We call an attribute an accident when it neither is necessary nor usually belongs to a thing, yet does in fact belong to it.”

— Aristotle, Metaphysics V.30, 1025a14–16

Here συμβεβηκός designates a feature that can attach or fail to attach to a subject without affecting what it is.

Contexts of Use in Aristotle

Aristotle employs κατὰ συμβεβηκός in several contexts:

In Categories 2, he distinguishes what is said of a subject or present in a subject per se from what is present only incidentally. In Metaphysics V and VI, he lists “accidental being” as one of several senses of being, considered the most derivative. In Physics II.4–6, he introduces τυχή (chance) and αὐτόματον (spontaneity) as modes of causation “by accident” (κατὰ συμβεβηκός) relative to final and efficient causes.

From Greek to Latin

Late antique commentators (Alexander of Aphrodisias, Themistius, Simplicius) elaborate the notion of συμβεβηκός, emphasizing its non‑essential character and its dependence on substances. When Aristotle is translated into Latin, κατὰ συμβεβηκός becomes per accidens, and τὸ συμβεβηκός becomes accidens, fixing the terminological pair that medieval scholastics will systematically develop.

This Greek background anchors the later Latin use of per accidens as a cross‑cutting category for accidental predication, accidental being, and accidental causation, all defined negatively with respect to what belongs to a thing καθ᾽ αὑτό, “in itself.”

4. Pre-Philosophical and Everyday Usage

Before its crystallization as a technical term, the conceptual content later expressed by per accidens and κατὰ συμβεβηκός is present in ordinary language about things that “happen to” subjects without defining them.

Everyday Greek and Latin Background

In everyday Greek, συμβαίνειν means “to happen” or “to occur,” and speakers could describe an event as something that “befalls” a person or thing, often with connotations of contingency. Similarly, in Latin, verbs like accidere and nouns like casus or fortuna were used in non‑technical contexts:

These expressions do not yet distinguish clearly between “incidental but regular” and “rare or random,” a distinction that later philosophical usage will sharpen.

Intuitive Distinctions in Common Thought

Ordinary speakers distinguish intuitively between:

• What something is (its kind or nature: “a horse,” “a man”), and
• What “happens to be the case” about it (its changeable features: “tired,” “wet,” “lucky”).

This folk contrast underlies later technical talk of essence versus accident. For example, that a person is tall or wealthy is typically understood as something that can change without the person ceasing to be the kind of thing they are.

From Pre‑Philosophical to Technical Usage

When Aristotle and subsequent philosophers systematize this everyday contrast, they transform diffuse intuitions into sharply defined categories:

• The ordinary idea that something may “just happen” without being part of a thing’s nature becomes the basis for συμβεβηκός / accidens.
• The everyday sense that some descriptions capture “what it really is” becomes the basis for talk of essence and per se predication.

In this way, pre‑philosophical usage provides the semantic and experiential soil from which the more precise distinction between per se and per accidens grows, even though the fixed Latin phrase per accidens itself is primarily a product of scholastic philosophical Latin rather than colloquial speech.

5. Aristotle’s Foundational Distinction

Aristotle articulates the foundational contrast between per se (καθ᾽ αὑτό) and per accidens (κατὰ συμβεβηκός) across predication, being, and causality. Later Latin authors mirror this structure with per se and per accidens.

Per Se vs Per Accidens Predication

In works such as Categories and Posterior Analytics, Aristotle distinguishes:

In the stock example, “the musician builds a house,” the true underlying subject is “the builder,” and “musician” is an incidental attribute. The predication “the musician builds” is per accidens because being a musician is not what makes house‑building possible.

Accidental Being (Ens per accidens)

In Metaphysics V.30 and VI.2, Aristotle lists accidental being as one sense of “being”:

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“We call ‘being’ in one sense what is accidentally, and in another what is in the sense that something is true…”

— Aristotle, Metaphysics VI.2, 1027a10–12

Accidental being includes conjunctive entities like “the musical man” or coincidental events like “a man hitting upon a treasure while digging a ditch.” These have no unified essence over and above their components.

Per Accidens Causality in Physics II

In Physics II.4–6, Aristotle discusses chance (τυχή) and spontaneity (αὐτόματον) as forms of causation κατὰ συμβεβηκός. A chance event occurs when an intended goal is realized by processes ordered to another end—for example, someone going to the market to sell goods but thereby meeting the person they wanted to see.

The cause is per accidens because the outcome does not proceed from the agent or process qua ordered to that result. This introduces a distinction between:

Aristotle tends to assign lesser explanatory weight to per accidens being and causality: they are real, but derivative and indeterminate, standing in contrast to the more fundamental per se structures that ground scientific knowledge and metaphysical analysis.

6. Per Accidens in Medieval Scholastic Logic

Medieval logicians adopt per accidens primarily to classify kinds of predication and inference that do not track essential connections. This usage is closely connected to, though distinct from, its metaphysical applications.

Accidental Predication in Logical Theory

Authors such as Peter of Spain and William of Ockham distinguish between essential and accidental predication in their treatments of categorical propositions:

A predication is per accidens when removing the predicate does not destroy the subject as such; it concerns what can vary while the subject remains of the same kind.

Per Accidens Propositions and Inferences

In medieval logical handbooks, propositiones per accidens and consequentiae per accidens are contrasted with per se or “formal” propositions and consequences:

• A per accidens proposition may be true only under certain contingent conditions, because the predicate is not tied to the subject’s nature.
• A per accidens consequence is one whose validity depends on factual connections or background assumptions, not solely on the logical form or essential content of the terms.

For instance, from “Every swan is white” to “Every swan is colored,” some authors classify the inference as per accidens: “white” implies “colored” only given contingent facts about colors, not purely from the essence of swanhood.

Demonstration and Scientific Knowledge

Building on Aristotle’s Posterior Analytics, scholastics often reserve scientific demonstration for per se connections. Per accidens propositions and inferences are held to be:

• Less suitable as middle terms in demonstration,
• Non‑convertible or only conditionally convertible,
• Dependent on extrinsic or empirical correlations.

Proponents argue that this logical categorization preserves the distinction between knowledge of causes (per se, demonstrative) and knowledge of coincidental conjunctions (per accidens, non‑demonstrative), a distinction that will inform scholastic accounts of science and epistemology.

7. Per Accidens in Metaphysics and Ontology

In scholastic metaphysics, per accidens is applied to modes of being and unity. It characterizes entities whose unity is not grounded in a single essence or substantial form, but in aggregation, conjunction, or incidental association.

Ens per Accidens

Many scholastics distinguish between:

Ens per accidens lacks a unified essence distinct from its components. A “white man” is not a new substance beyond “man” and “white”; its being is derivative, grounded in the substance and its accident.

Some authors further classify:

• Per accidens unities such as “an army and its general passing by,” or
• Temporal conjunctions like “a builder and an eclipse occurring simultaneously.”

These are said to be “one” only in a loose, extrinsic sense.

Ontological Status and Debates

Scholastics diverge on the metaphysical weight accorded to ens per accidens:

• Some, following an Aristotelian line, treat it as a weak, derivative mode of being, primarily a façon de parler for underlying substances and accidents.
• Others, especially in late scholasticism (e.g., Suárez), give more systematic accounts of such unities, distinguishing between:
  • Real but non‑essential aggregates (e.g., a heap of stones),
  • Mere beings of reason (entia rationis) that exist only in thought, and
  • Mixed cases where conceptual grouping tracks real relations.

Debate centers on whether per accidens unities enjoy any intrinsic ontological grounding beyond the realities of their constituents. Proponents of a more robust view emphasize the explanatory role of complex wholes in causality and cognition; more austere metaphysicians insist that only substances and their proper accidents are ontologically fundamental.

Relation to Substance and Accident

Across these positions, a common framework holds:

• Substance is the primary bearer of being and unity.
• Accidents inhere in substances but do not themselves constitute independent substances.
• Ens per accidens names configurations whose being and unity reflect the co‑presence of a substance with one or more accidents, or of several substances together, without a further unifying form.

This ontological use of per accidens complements its logical and causal applications, all structured by contrast with what belongs per se to a thing’s nature.

8. Per Se vs Per Accidens Causality

In Aristotelian and scholastic accounts of causation, per accidens qualified causes are contrasted with per se causes in terms of how directly and essentially they are ordered to their effects.

Per Se Causality

A cause is per se when its effect proceeds from it as such—from its nature or from an intrinsic ordering to that effect. For example:

• Fire heating is per se causality, since heating follows from fire’s nature.
• A physician healing, considered as physician, is per se relative to healing.

Per se causation typically grounds explanatory necessity: the effect follows given the cause and suitable conditions.

Per Accidens Causality

A cause is per accidens relative to an effect when the effect arises from features that are incidental to the cause’s primary nature or to its intentional aim. Examples drawn from scholastic texts include:

Here the causal line runs primarily through the man as generator, the agent as builder, or the walk as such; the additional features are causally irrelevant or only indirectly relevant.

Relative and Context‑Dependent Character

Scholastic authors emphasize that the distinction is relative to the description under which a cause is considered. The same concrete agent may be:

• A per se cause of one effect (the physician as healer),
• A per accidens cause of another (the same physician as musician causing healing).

This relativity leads to debates about:

• Whether per accidens causes have any genuine causal efficacy or merely describe coincidental features of per se causes.
• How far per accidens causality can figure in scientific explanation, as opposed to anecdotal or narrative description.

In general, per accidens causality is accorded a lower explanatory status: it is acknowledged as real in some sense but regarded as less fundamental than per se causality for understanding the ordered structure of nature.

9. Major Thinkers’ Definitions and Debates

Across the Aristotelian–scholastic tradition, key figures define per accidens in related but distinct ways, often emphasizing different domains.

Comparative Overview

Aristotelian and Thomistic Lines

Following Aristotle, Aquinas describes per accidens predication as attributing accidents that do not arise from a subject’s essence, and per accidens causes as those whose effect does not proceed from the cause’s own proper power. Aquinas frequently uses examples like “a white man generates a white son,” emphasizing that whiteness is extrinsic to the generative power.

Some Thomists stress that for Aquinas:

• Per accidens refers both to logical (predicative) and real (causal, ontological) structures.
• The per accidens / per se contrast is central for differentiating scientia (science) from mere empirical generalization.

Logical Traditions

Authors such as Peter of Spain and Ockham highlight per accidens as a property of propositions and inferences. They often treat it as a formal criterion: the proposition “Socrates is white” is per accidens not because of any empirical frequency but because “white” is logically removable without altering the subject’s sortal status.

Debates here concern:

• Whether per accidens consequences can be strictly valid, or only materially true given extra‑logical facts.
• How per accidens predication should be classified in syllogistic figures and conversions.

Suárez and Late Scholastics

Suárez develops a nuanced account of ens per accidens and accidental causal series, distinguishing:

• Essentially ordered series (per se), where later causes depend here and now on earlier ones.
• Accidentally ordered series (per accidens), where causes do not require the continued activity of predecessors once they exist.

He also discusses whether per accidens beings possess any distinct unity and how to categorize them relative to substances and accidents.

Neo‑Scholastic and Contemporary Debates

Modern Thomists and analytic interpreters focus particularly on:

• The status of per accidens causal series in cosmological arguments.
• Whether classical texts support a strong metaphysical contrast between temporal and hierarchical orders.

Some argue that traditional sources sharply differentiate accidentally ordered, temporally extended series from essentially ordered, hierarchical ones; others contend that the historical evidence is more ambiguous and that later reconstructions may over‑systematize diverse medieval views.

10. Logical and Epistemic Implications

The per se / per accidens distinction has significant implications for logic and theories of knowledge, particularly in the Aristotelian–scholastic framework of science as demonstrative knowledge of causes.

Demonstration and Scientific Knowledge

Following Aristotle’s Posterior Analytics, scholastics typically hold that:

• Per se connections are suitable for scientific demonstration, because they reveal why things must be so.
• Per accidens connections cannot ground the strictest form of scientific knowledge, since they lack necessity and often generality.

For example:

Per accidens propositions may be true and useful but are often classified as non‑demonstrative or only empirically confirmed.

Structure of Inference

The classification of propositions as per se or per accidens informs:

• Which middle terms are admissible in syllogistic proofs,
• How far conversion and subalternation can be applied,
• When an inference counts as formally valid versus materially acceptable.

Per accidens inferences often rely on extrinsic correlations; if those correlations change, the inference no longer holds, indicating that its necessity is not logical but factual.

Epistemic Status of Accidental Truths

Scholastics distinguish between:

Accidental truths—such as that this particular person is currently sitting—are knowable but do not typically figure in the highest level of theoretical explanation. Some authors discuss how induction from per accidens observations might still reveal per se structures, while warning against conflating stable correlations with essential connections.

In later epistemology, the per accidens category becomes a tool for distinguishing merely concomitant features from those that genuinely explain phenomena, shaping discussions about the difference between law‑like generalizations and accidental generalities.

11. Relations to Contingency, Chance, and Fortune

The notion of per accidens intersects with, but is not identical to, concepts of contingency, chance, and fortune. Scholastic authors often refine these relationships to avoid conflating distinct modal notions.

Per Accidens and Contingency (Contingens)

A property or event can be:

• Per accidens: non‑essential to its subject or cause.
• Contingent (contingens): capable of being otherwise, not necessary.

While many per accidens features are contingent (e.g., a man’s being sun‑tanned), the categories do not always coincide. Some accidental attributes may be regular or even necessary given certain conditions (for example, color patterns that necessarily follow from particular material arrangements), yet remain non‑essential to the substance in question.

Chance (Casus, τύχη) and Spontaneity (Fortuitus, αὐτόματον)

In Physics II, Aristotle characterizes chance (τυχή) and spontaneity (αὐτόματον) as forms of causation κατὰ συμβεβηκός, i.e., per accidens:

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“Chance and spontaneity are causes in the sense in which the cause per accidens is a cause.”

— Aristotle, Physics II.5, 197b15–17

Latin and scholastic vocabulary mirrors this:

Not every per accidens occurrence is a chance event in this strong sense; some are predictable side‑effects. Conversely, chance and fortune are usually analyzed as subspecies of per accidens causality, especially where an effect coincides with but is not aimed at by an agent.

Fortune and Human Affairs

In discussions of fortune (Latin fortuna), medieval and Renaissance authors often draw on the per accidens framework: fortunate events are those which, relative to human intentions and expectations, occur praeter intentionem and are beneficial. Their explanation invokes:

• The convergence of independent causal lines,
• The incidental realization of desirable ends.

Philosophical treatments then ask whether such events are genuinely uncaused (typically denied in Aristotelian–scholastic systems) or merely per accidens relative to human purposes while still per se with respect to broader natural or divine orders.

Overall, per accidens provides a structural vocabulary for analysing contingency, chance, and fortune, clarifying when an effect is incidental relative to a given cause, even if it is not absolutely uncaused or wholly random.

12. Comparative Concepts: Accident, Property, and Essence

The meaning of per accidens is best understood in relation to the triad essence, accident, and property (proprium) in Aristotelian and scholastic metaphysics.

Essence vs Accident

Essence (quidditas, essentia) is what makes a thing the kind of thing it is. Accidents (accidentia, accidens) are features that can be present or absent without changing the thing’s species.

A predicate is per accidens when it attributes an accident rather than the essence.

Property (Proprium)

A property (proprium) occupies a middle place:

• It is not part of the definition of the essence.
• Yet it necessarily accompanies members of a species (e.g., “capable of laughter” for humans in some accounts).

Propria are often associated with per se in a broad sense (sometimes labelled “per se in the second mode”), because they flow necessarily from a thing’s nature.

Per Accidens and the Ontology of Accidents

Given this framework, per accidens marks not only logical predications but also the ontological status of many accidents:

• They inhere in substances but do not determine the substance’s species.
• Their being is therefore dependent and derivative, corresponding to the notion of ens per accidens when considered in certain conjunctions (e.g., “the pale man”).

Debates arise over borderline cases, such as highly stable or natural accidents (e.g., typical color of a species), and whether these should be treated as properties (propria) or remain strictly per accidens.

Comparing these concepts clarifies that per accidens generally tracks the non‑essential, non‑necessary side of the essence/property/accident schema, while per se covers both essence itself and those properties that necessarily flow from it.

13. Translation Challenges and Strategies

Rendering per accidens into modern languages raises several difficulties, because no single term captures all of its technical nuances across logic, metaphysics, and causality.

Semantic Range vs Modern Connotations

In scholastic usage, per accidens:

• Can mean “non‑essentially” in predication,
• “Incidentally” or “indirectly” in causality,
• “As a mere aggregate or side‑effect” in ontology.

Modern English “accidentally” often suggests error or negligence (e.g., “accidentally dropped”), which is usually irrelevant to the scholastic sense. Likewise, “by chance” can connote randomness, whereas per accidens relations may be regular and predictable.

Common Translation Options

Scholars employ several strategies:

Many translators therefore leave per accidens untranslated, explaining it in glossaries, particularly in technical contexts (e.g., discussions of causal series).

Cross‑Linguistic Strategies

In modern European languages, parallel issues arise:

• French: par accident, accidentellement often carry everyday senses; some authors retain the Latin.
• German: zufällig maps to “contingent” or “by chance,” potentially overemphasizing randomness; scholars sometimes use “akzidentiell” as a technical borrowing.
• Spanish and Italian often use accidental(mente) but similarly rely on context and scholarly convention to signal the technical meaning.

Balancing Fidelity and Readability

Translators and commentators adopt different priorities:

• Some prioritize historical fidelity, preserving the Latin and Greek terms (per accidens, κατὰ συμβεβηκός) and providing explanations.
• Others aim for readability, choosing context‑specific paraphrases, even at the cost of strict uniformity.

These choices influence how contemporary readers understand the per se / per accidens distinction and can affect interpretations of arguments, particularly where fine distinctions between contingent, incidental, and chance are philosophically significant.

14. Per Accidens in Natural Philosophy and Science

In Aristotelian and scholastic natural philosophy, the per accidens category is used to distinguish essential laws and tendencies of nature from incidental or derivative features. This structure influenced early conceptions of scientific explanation.

Essential vs Accidental Features of Natural Kinds

Natural philosophers typically assume that each natural kind has per se properties and operations. Per accidens features are:

• Dependent on external conditions (e.g., climate effects on color),
• Or arising from non‑essential configurations (e.g., deformities, rare events).

For example, in Aristotelian biology:

Scientific explanations aim primarily at the per se characteristics (e.g., why animals of a certain type have specific organs), while per accidens traits are often relegated to case histories or pathology.

Per Accidens Causes in Physical Processes

In Physics II, Aristotle’s analysis of chance and spontaneous events as per accidens causes influences treatments of:

• Unusual meteorological phenomena,
• Monstrous births,
• Random collisions of bodies.

Such occurrences are explained by converging causal chains that, per se, are ordered to different ends but intersect in ways that generate novel, unintended outcomes. These are not outside nature but are side‑effects of regular processes.

Role in Early Scientific Method

Pre‑modern natural philosophy often holds that:

• Per se regularities form the core of scientific law, to be captured in universal statements.
• Per accidens phenomena are exceptions, anomalies, or boundary cases, which may still provide clues to underlying structures but do not themselves define the essence of a natural kind.

Some historians of science argue that this framework encouraged a focus on typical and regular phenomena and a relative neglect of statistical or probabilistic patterns, which tend to appear per accidens within the Aristotelian scheme. Others note that attention to per accidens events (e.g., eclipses, comets, rare diseases) also stimulated more detailed empirical investigation.

Transition to Modern Science

As mechanistic and probabilistic models emerged in early modern philosophy, the per se / per accidens distinction was reinterpreted or downplayed in some traditions. Nevertheless, the underlying concern—to separate core explanatory structures from incidental correlations—remains active in contemporary discussions of laws of nature, ceteris paribus clauses, and the distinction between law‑like and accidental generalizations.

15. Per Accidens Series in Cosmological Arguments

Within philosophical theology and metaphysics, per accidens is central to discussions of causal series in cosmological arguments, especially in Thomistic and Neo‑scholastic traditions.

Essentially vs Accidentally Ordered Series

A key distinction is drawn between:

In an accidentally ordered series, each cause can act independently once it has come into being; its causal power does not require the ongoing concurrence of earlier members of the series.

Role in Cosmological Arguments

Many interpreters of Aquinas and later Thomists hold that:

• Cosmological arguments for a first cause do not require denying an infinite per accidens series in time (e.g., an infinite chain of generations).
• The argument instead targets per se series, claiming that such hierarchically ordered causal chains must terminate in a first, non‑derivative cause.

Per accidens series are thus used to clarify the scope of cosmological reasoning: if only essentially ordered series demand a first cause, then the possibility of an infinite temporal regress of per accidens causes is not, by itself, incompatible with a first cause argument.

Interpretive Controversies

Scholars differ on several points:

• Some argue that classical authors clearly distinguish these two types of series and restrict the demand for a first cause to per se series.
• Others contend that the historical texts are more ambiguous and that later Thomists may have sharpened the distinction in light of debates about the eternity of the world and modern notions of infinite regress.
• There is also discussion over whether some supposed examples of per accidens series (e.g., biological propagation) might covertly involve deeper per se dependencies (e.g., on continuous sustaining causes).

In contemporary analytic philosophy of religion, the language of accidentally ordered causal series is often retained, with per accidens serving as a technical label for series where temporal succession does not entail ongoing hierarchical dependence, thereby framing the structure of certain cosmological arguments.

16. Neo-Scholastic and Contemporary Reinterpretations

Neo‑Scholastic thinkers in the 19th and 20th centuries, along with contemporary analytic Thomists, revisit per accidens to address modern philosophical concerns and scientific developments.

Neo-Scholastic Systematization

Neo‑Scholastics such as Garrigou‑Lagrange and manuals of Thomistic philosophy standardize:

• The causal series distinction: per se vs per accidens, often illustrated with canonical examples.
• The use of per accidens to classify contingent, non‑essential properties in discussions of essence and existence.
• The appeal to per accidens in arguments about contingent beings and cosmological dependence.

These authors tend to present the per se / per accidens framework as a general metaphysical tool, applicable across ontology, epistemology, and natural theology.

Engagement with Modern Science and Metaphysics

In light of modern physics and biology, some Neo‑Scholastics and contemporary Thomists:

• Reinterpret per accidens causality in probabilistic contexts, discussing whether stochastic processes are best treated as per accidens relative to deeper, per se structures.
• Re‑examine ens per accidens in relation to systems theory or emergent properties, debating whether certain complex wholes have only accidental unity or a more robust, quasi‑essential organization.

Different authors propose:

Analytic Thomism and Formal Reconstruction

Analytic Thomists (e.g., some contemporary Anglophone philosophers) have:

• Formalized the per se / per accidens distinction using tools from modal logic, causal modeling, or mereology.
• Debated whether per accidens generalizations can count as laws of nature or only as accidental generalizations.
• Explored per accidens structures in relation to essentialism and dispositional properties, asking how essential dispositions differ from accidental capacities.

Some critics question whether the traditional distinction maps neatly onto contemporary metaphysical debates (e.g., between internal and external relations), while proponents argue that it continues to illuminate differences between deep explanatory connections and surface correlations.

Overall, Neo‑Scholastic and contemporary reinterpretations treat per accidens as a flexible but structured concept, seeking to preserve its historical roles while adapting it to modern scientific and philosophical contexts.

17. Legacy and Historical Significance

The concept of per accidens, together with its counterpart per se, has had a lasting impact on the history of philosophy, shaping views on essence, causality, and scientific explanation.

Structuring Classical and Medieval Thought

In the Aristotelian–scholastic tradition, the per se / per accidens pair provides a unifying framework across:

• Logic: distinguishing essential from accidental predication and demonstrative from non‑demonstrative inferences.
• Metaphysics: clarifying the hierarchy of being, from substances and their essential properties to accidental aggregates and side‑effects.
• Natural philosophy: ordering causes and effects, and separating core regularities from incidental phenomena.

This framework influenced curricula in medieval universities, commentaries on Aristotle, and the construction of comprehensive philosophical systems by thinkers such as Aquinas and Suárez.

Influence on Early Modern and Later Philosophy

While some early modern philosophers rejected or revised Aristotelian metaphysics, elements of the per accidens distinction persisted:

• In debates about essential vs accidental properties (e.g., in Leibnizian and later essentialism),
• In discussions of law‑like vs accidental generalizations in philosophy of science,
• In ongoing reflections on chance, fortune, and the explanation of anomalous events.

Even where the Latin terms disappear, the underlying questions about what belongs to things in themselves versus what happens only incidentally remain central.

Contemporary Relevance

In contemporary metaphysics and philosophy of religion, per accidens continues to be cited:

• In reconstructions of cosmological arguments, especially regarding accidentally ordered causal series.
• In historical exegesis of Aristotle and scholastic authors, where understanding per accidens is crucial for accurate interpretation.
• In debates about essentialism, dispositions, and laws of nature, where distinctions between essential connections and accidental correlations are re‑examined with new tools.

The enduring significance of per accidens lies less in any one specific doctrine than in its role as a conceptual lens for analyzing the difference between what is grounded in nature or essence and what arises through conjunction, context, or coincidence—a distinction that continues to inform philosophical inquiry across historical periods.