Abstract

In a number of texts throughout his career, Thomas Aquinas identifies different senses of the term ‘esse’. Most notably, he notes that according to one sense, the term signifies the act of existence (actus essendi), which he famously holds is really distinct from essence in all beings other than God. Perhaps surprisingly, he also notes on a number of occasions that according to another sense, the term ‘esse’ can signify that very principle that he says is distinct from the act of existence, namely, essence. In light of Aquinas's semantic theory, this paper investigates how he coherently holds within his metaphysical system that this term ‘esse’ can signify in different ways both essence and the act of existence. More broadly, what it shows is how, for Aquinas, the metaphysician can look to the modes of signification (modi significandi) of terms and as well as their modes of predication (modi praedicandi) to draw careful conclusions about the modes of existence (modi essendi) of real beings. These considerations reveal that in Aquinas's view, although the grammarian and logician in their way are also concerned with these semantic modes, it is not their job to employ them to discern the various senses of the term ‘being’ or the fundamental modes of being. In the end, this is a task for the metaphysician.