Paul Kucharski
Fordham University
In chapter four of On Being and Essence, Thomas Aquinas argues that immaterial substances, despite being free from matter, are not pure acts because their essence is in potency to the act of existence, and it is here that he introduces his account of the real distinction between esse (existence) and essence. In both immaterial and material substances, he thinks, we find a real distinction and composition of esse and essence; only in God are these principles identical.
Aquinas’s notion of the real distinction is one of his most important metaphysical doctrines, because it allows him to prove the existence of God and to state precisely the manner in which God differs from all other beings. Aquinas’s argument for the real distinction has been subjected to much scrutiny and criticism. Scholars disagree as to whether or not he establishes the real distinction. Among those who think that Aquinas’s argument is successful, there is disagreement as to exactly where in the chapter four passage the real distinction is established. Some argue that the intellectus essentiae argument, where Aquinas states that an essence can be fully understood apart from existence, is enough to establish the real distinction. Others claim that the following passage, where Aquinas argues that there can only be one possible being whose esse and essence are identical, is needed in addition to the intellectus essentiae argument. Finally, there are those who claim that only after Thomas proves the actual existence of a being whose essence is esse can we accept the real distinction. In this paper, I argue that Aquinas does establish a real distinction between esse and essence. I also argue that the intellectus essentiae argument is sufficient for establishing the real distinction in material substances; the second and third stages of the chapter four passage are required to establish the real distinction in all substances (including immaterial substances) and to prove the existence of the first cause of the esse found in creatures.
I begin by examining Anthony Kenny’s critique of the real distinction as found in Aquinas on Being. Kenny argues that at best Aquinas’s argument for the real distinction establishes the following: I can understand a concept without knowing whether or not the concept is instantiated. It fails to establish esse and essence as two distinct metaphysical co-principles. Further, given the Fregean understanding of existence (“Xs exist” = “Something is X”) that he endorses, Kenny argues that the real distinction argument makes unintelligible Aquinas’s depiction of God as ipsum esse subsistens. I argue that Kenny’s critique falters because he fails to understand Aquinas’s conceptual framework and how Aquinas uses terms like “essence” and “existence.”
I then examine three different interpretations of the real distinction argument as put forth by Joseph Bobik, John Wippel, and Joseph Owens. In Aquinas on Being and Essence, Bobik argues that the intellectus essentiae argument is sufficient for establishing the real distinction in material beings, because the essence of a thing is both the principle by which a thing exists independently of human knowledge and the principle by which a thing is intelligible. Therefore, if essence is other than esse in the order of knowledge, then the two are distinct in the order of reality, as well. In “Aquinas’s Route to the Real Distinction,” John Wippel argues that the intellectus essentiae argument only establishes a difference between the knowledge of what something is and the knowledge that something exists. It is only in the following passage, when Aquinas argues that a being whose essence is esse must be unique, that the real distinction is established, for then we can say that in all other beings there must be an ontological distinction between essence and esse. Finally, Joseph Owens, in “Quiddity and the Real Distinction in Aquinas,” argues that only when Aquinas proves the actual existence of a being whose essence is identical to its esse does he establish the real distinction, because only then do we recognize existence as a real nature that can be distinct from essence.
I defend Bobik (though not uncritically) and argue that the intellectus essentiae argument is sufficient for establishing the real distinction in material substances. Wippel and Owens, like Kenny, misstep when they interpret the intellectus essentiae argument as beginning solely in the conceptual realm. I argue that this occurs because they fail to appreciate Aquinas’s understanding of essence as that which is only properly said of real beings, and perhaps because they are mislead by Aquinas’s example of the phoenix. I maintain that there are historical and philosophical reasons to suppose that Aquinas does not begin his argument for the real distinction with both real and imaginary essences, and therefore there is no reason to interpret his argument as beginning with a conceptual distinction.