Accidentally Ordered Causal Series

Accidentally Ordered Causal Series

Principal locus	Summa theologiae I, q. 46, a. 2 ad 7; q. 7, a. 4
Definition	A causal succession in which a later cause exercises its power without the continued causal action of earlier members
School	Thomism
Branch	Thomistic philosophy
Status	Thomistic metaphysical distinction

An accidentally ordered causal series, traditionally called a per accidens or linear series, is a succession in which a later cause can exercise its own causal power after an earlier member has ceased to act or exist. A father begets a son who later begets another child; the grandfather need not be presently generating for his adult son to do so. Accidental here does not mean random, uncaused, or unimportant. It means that the earlier member's continued causal influence is not essential to the later member's current exercise of the power in question.

Theological status: Theological synthesis

Succession rather than present instrumentality

In an accidental order, the earlier cause accounts for how a later cause came to possess a power, but it does not supply that power instrumentally during each later exercise. Parents generate a child; once mature, the child can generate even after the parents have died. One hammer may break and be replaced by another. The first hammer's present motion is unnecessary for the replacement tool to strike. These examples contrast with the stick that moves only while the hand applies it.

The distinction always concerns a specified causal respect. A son depends historically upon his father for generation, yet his present existence depends essentially upon God's conservation. A hammer does not depend on an earlier hammer to drive a nail, but it depends on a present principal agent to act as an instrument. Calling a series accidental therefore never asserts absolute independence. It identifies one relation in which causal succession does not constitute a here-and-now hierarchy of borrowed action.

Why accidental does not mean chance

Scholastic accidental predication often means that something falls outside the formal account under consideration. The grandfather's continued existence is accidental to the grandson's generative power: it may be biographically precious and causally relevant in many other respects, but it is not part of what makes the adult grandson generate here and now. Likewise, the succession of craftsmen who manufactured tools may be historically necessary without entering the present instrumental order by which one carpenter makes a table.

This use must not be confused with an uncaused event, a coincidence, or Aristotle's discussion of chance. Members of an accidentally ordered series have causes and may be governed by Providence. Their linear arrangement simply does not explain present causal efficacy through the simultaneous derivation characteristic of essential order. The adjective marks the relation of the members to the act being analyzed; it does not offer a verdict that the events lack purpose, intelligibility, or divine governance.

The qualified possibility of an infinite series

Aquinas allows that an infinite regress is not excluded in an accidentally ordered series by the same demonstration that excludes it in an essential order. If one human generates another, each generator acts through a power possessed as its own created form, not merely as the current instrument of the preceding parent. Postulating earlier generations does not leave the present parent without a proximate generative power. An indefinite extension of that history is therefore a different philosophical question from whether derivative causal action has a first source.

This is a qualified logical and metaphysical point, not Aquinas's assertion that there actually has been an infinite human genealogy. Biological conditions could prevent that particular example from extending without limit. More importantly, every member—however many—would still depend upon God for being and operation. An infinite accidental succession would not replace primary causality, because adding predecessors does not explain the present existence or causal actuality of any member. The two questions operate at different levels.

Creation in time and natural reason

Catholic faith confesses that the world was freely created by God and has a beginning. Aquinas nevertheless argues in Summa theologiae I, question 46, article 2 that a temporal beginning cannot be demonstrated from the nature of created things. It is known by revelation. His reply to objection 7 expressly separates the impossible infinite regress of causes required per se for one effect from an accidental infinity of agents, as when one generator succeeds another.

The distinction makes Aquinas's position unlike both a simple temporal first-cause argument and an eternalist denial of creation. He accepts the revealed beginning without claiming a philosophical proof he judges invalid. At the same time, his demonstrations of God's existence do not wait upon that beginning, because an eternal created order would still be dependent. The Creator is first as the source of being and causal actuality, not merely as an event located before all other events.

Contrast with essential order

A per se series can be represented by principal agent, living power, instrument, and present effect; remove every principal source of the derivative action and nothing in the series acts. A per accidens series can be represented by predecessor and successor; once the successor possesses the relevant power, the predecessor need not continue to exercise it. The contrast explains why endlessly multiplying instruments does not solve the first series, while merely extending ancestry does not create the same immediate defect in the second.

Careful Thomistic argument names the order rather than using chain of causes ambiguously. Historical causes, sustaining causes, material conditions, and instrumental causes can intersect in one event. A manuscript may depend historically upon generations of scribes, materially upon parchment, presently upon conservation in being, and instrumentally upon a writer's hand and pen. Classifying one sequence as accidental does not dismiss the other causes. It prevents a temporal narrative from being mistaken for the metaphysical hierarchy the first-cause demonstration addresses.