44. The Doctrine of Causes. -- The theory of causes is closely connected with that of motion; for the term "cause" is applied to whatever exercises any real and positive influence on the actuality of a being at any stage whatever of its development. Aristotle distinguishes four causes, the material, the formal, the efficient, and the final.

(1 and 2) Material and Formal Causes. -- Primal or primary matter and substantial form, which are the constitutive elements of being, are also, under another aspect, its causes; for their union gives rise to the substantial compound. Material and formal causes are of the accidental order when they constitute a mode of being of something already supposed to be complete substantially.

(3) Efficient or Moving Cause -- A substantial compound, or any one of its stages, is realized by its passing from power to act. But nothing that is moved moves itself, hapan to kinoumenon anagkê hupo tikos kineisthai (Phys., vii., 1). For what is merely in potentiality does not, as such, contain the sufficient reason of its own actualization. Therefore the transition from power to act, or from matter containing a form potentially to matter actually determined by that form, demands the influence of a moving cause, which latter could not influence or move the former unless it were itself in act. By reason of its continuous influence (thixis), this cause is the principle of all evolution in matter: the efficient cause, or more properly speaking, the motive cause (to d' hothen hê kinêsis).^{1}

Aristotle, therefore, confines efficiency to the production of movements or changes, and these follow a real, internal virtuality or tendency of the matter to unite with the form that corresponds to the natural exigency of the compound. But the chain of changes has never had a beginning and can never have an end: motion is eternal. So also is matter, the substrate of all change: matter is simply there, though never produced, nor does Aristotle account for its existence.^{2}

(4) Final Cause. -- The co-ordination of activities in the things of Nature, and the stability of the universal order to the realization of which every single thing in the cosmos contributes something, are indications that the substantial forms of things are endowed with an intrinsic tendency towards some end which draws out their latent energies (final cause). This notion of purpose, design, finality, is of fundamental importance in Aristotle's metaphysics. It justifies and explains for him the regular recurrence of natural phenomena and the fixity of natural kinds in the domain of physics, the innate tendency of the mind towards truth in criteriology, the inclination of the will towards the good in ethics.

{1} In modern scientific language a motor or moving cause denotes merely a cause productive of local movement. We use the term here in the wider sense of Aristotle, as the cause of any change whatever.

{2} In certain passages Aristotle places the reality, the finality and all the intrinsic activities of the being in its form; and in the ambiguous language he uses, some historians, notably ZELLER (op. cit., ii., 2, p. 328), wrongly think they see traces of a confusion of the three causes, -- formal, final, and efficient or motor cause.