We gave an introductory teaser to this issue HERE.
We now continue:
The philosopher Heidegger has stated that the problem in metaphysics is that we have constantly asked “what it is” but have neglected to ask what about “that it is.” Why should there be anything at all? We might say that we can understand the essence of a horse and the essence of a unicorn, but there are horses and there do not seem to be unicorns, so the essence and knowledge of it does not make a thing to actually exist.
Aristotle’s god (or gods) did not cause the being of all that exists, but merely are the primary and unmoved mover. For Aristotle, the fact that things “are” seems to be a given. Of course, it is true that things “are,” but their existence is not the explanation for their existence. Otherwise, they would not be contingent beings. This seems to go hand in hand with Aristotle’s (supposed) proofs of the eternity of the universe. The universe simply is. Bertrand Russell and the majority of modern materialists as well seem to agree. We should not, then, look for a cause of things, but accept that “things are” as our starting point.
The doctrine of creation ex nihilo seems to be the key to the philosophical discovery of the distinction between essence and existence. If things “began to be” then their existence is not explained by their essence. The reason that horses “are” and that unicorns “are not” cannot be simply explained by evolution, for example. Evolution may explain why unicorns “are not” but it only a partial explanation of why horses “are.”
Evolution, as one theory, can explain why horses “are what they are” and why they are not unicorns, but it offers no explanation as to why there are horses instead of nothing at all. An eternal world might seem at first to get rid of this problem, but even in an eternally existing world, once looked at deeper, the problem remains. As Thomas Aquinas shows, the doctrine of an eternally existing world, although contrary to revealed truth, does not deny the possibility of creation ex nihilo. The existence of anything contingent, whether eternal or not, still requires a cause, even if not a cause prior in time.
This cause, however, being uncaused (for otherwise we have the impossible infinite regress) is of necessity the explanation of its own existence. This is not to be confused with being the cause of its own existence, for it is not caused. Therefore, this uncaused cause is a “something” and whatever this is is its essence. But it is also its very existence, for that is the only way for it to be uncaused.
Without going through all the attributes of this uncaused cause as examined by Aquinas, we must say here that its simplicity, its being pure act and having no potency, all tie into its very essence being “to be.” All else, then, besides God, is not “to be” but must receive its “to be” from outside of itself.
We can see, therefore, that in metaphysics and natural theology, the distinction between essence and existence is of utmost importance. And it seems to be that from the very revealed truth of God Himself saying to Moses that His name is basically “He that Is” is the key to this discovery.
Aquinas’ distinction here is important for understanding that God is outside of any genus.
Aristotle certainly did not teach this, at least not in any explicit way. The great Arabic metaphysicians like Avicenna certainly did not see this. In fact, it is likely that, for Avicenna, God is a being, and the only being, with a “specific difference” of “necessary.” He is, then, a universal species and the sole being of that species.
But for Aquinas this is not so. God stands outside of genus, and being is not a genus, for it has no “specific difference.” Being is predicated of all things, of both God and all contingent beings, but analogously.
Although not written by Thomas himself, we must list here the first 4 of the 24 Theses of Thomism, which make explicit the basic point we have been reviewing:
1. Potency and Act divide being in such a way that whatever is, is either pure act, or of necessity it is composed of potency and act as primary and intrinsic principles.
2. Since act is perfection, it is not limited except through a potency which itself is a capacity for perfection. Hence in any order in which an act is pure act, it will only exist, in that order, as a unique and unlimited act. But whenever it is finite and manifold, it has entered into a true composition with potency.
3. Consequently, the one God, unique and simple, alone subsists in absolute being. All other things that participate in being have a nature whereby their being is restricted; they are constituted of essence and being, as really distinct principles.
4. A thing is called a being because of being (“esse”). God and creature are not called beings univocally, nor wholly equivocally, but analogically, by an analogy both of attribution and of proportionality.
A rejection of this analogous use of being and a rejection of the real distinction between existence and essence is seen in thinkers after Aquinas as well, even among Christian thinkers such as Scotus. It has in no way been simply accepted after Aquinas, even by those who may agree with him on much else.
Nevertheless, although not explicitly endorsed by the church, for “The Church has no philosophy of her own nor does she canonize any one particular philosophy in preference to others,” (FR 49) the philosophy of Thomas Aquinas is considered the “perennial philosophy.” Pope Leo XIII promulgated the encyclical Aeterni Patris and this document provided for the revival of Thomism as practically the official philosophical and theological system of the Church. It was to be normative not only in the training at seminaries but also in the education at Catholic universities.
Although the Angelic doctors contributions the philosophy and theology are almost endless, it is hard to deny that his exposition of the distinction between essence and existence and the fact that these two differ in all but God is arguably the single most important key doctrine that he has left us.