288. Essence and Existence. -- This kind of composition, left untouched by Aristotle, now becomes the object of fine and delicate discussions. The terms of the debate are not the respective CONCEPTS of essence and existence, nor a POSSIBLE essence on the one hand and an EXISTING ESSENCE on the other: all recognized a real distinction between the terms of each of those comparisons. But, following up the analysis, they asked the question whether IN ANY ONE ACTUAL BEING its fundamental constitutive reality is one thing ("essentia, quod est"), and the act or actuality by which that reality exists, another thing ("esse, quo est").

Opinions differed. St. Thomas held a real distinction, the substance of his teaching being that existence is of the essence of God alone, the Pure Act. In creatures, on the other hand, whether material or spiritual, the perfection siginified by the word EXIST is contracted and circumscribed within the limits of the essence which it determines.^{1} Essence is to existence as potency is to act.^{2} But being becomes actual only in the measure in which it is capable of actuation; for the degree of being is measured by its connatural potency. Therefore a contingent essence can receive existential actualization only within the limits of its own contingency.

This theory is no special discovery of St. Thomas. We meet it frequently among the representatives of the older scholasticism.^{3} But none penetrated its meaning so deeply as he. And when we consider the general structure of Thomism, we cannot help being struck at the organic and unifying role played by this thesis in connection with the other leading theories of scholasticism. The real distinction between essence and existence places in bold relief the contingency of the creature; it accounts for the existential unity of beings that are composed of matter and form -- consubstantial principles, severally incomplete and mutually irreducible, -- and of beings that exert their activities by means of faculties really distinct from one another.

{1} "Unde esse earum non est absolutum sed receptum, et ideo limitatum et finitum ad capacitatem naturae recipientis" (De Ente et Essentia, cap. 6).

{2} See Cajetan, commentary on this passage.

{3} See SCHINDELE'S Dissertation, quoted 310. This writer believes St. Thomas drew from Pseudo-Denis and Boethius (p. 9). We may note that if the idea of the participation of being is found in Pseudo-Denis there is no trace of a comparison of essence with existence.