Thomas Aquinas on Necessary Truths about Contingent Beings

The aim of this dissertation is to give an account of Aquinas's thinking on the ontological grounds of necessary propositions about creatures. The kind of necessary propositions that this dissertation concerns are essential propositions, such as Man is an animal or Dogs are sentient. Throughout his works Aquinas affirms that every truth asserted by the human intellect is adequated to or conforms to some res. Accordingly, it seems that if necessary propositions are true at all times, then there must be some res that exists at all times to which these necessary propositions conform. Since both creatures and their essences are contingently existing beings that come to be and perish in time, many have concluded that the creatures themselves or their essences cannot be the res to which necessary propositions about creatures conform. It seems for example, that the proposition Dodo birds cannot fly cannot be grounded by dodo birds or their essences since both dodo birds and their essences ceased to exist almost four hundred years ago and still this proposition remains true. Various interpreters of Aquinas's thought have argued that some feature of God, such as his power or essence, grounds necessary propositions about creatures. In this dissertation, I argue for alternate interpretation of Aquinas. I make a textually based argument for the conclusion that Aquinas held that necessary propositions about creatures have their ontological grounds in the contingently existing substantial forms of the created beings themselves. The precise feature of a substantial form that guarantees the truth of a necessary proposition is its unicity. Aquinas thought that Man is rational is necessarily true because man and rational signify one form in reality. In addition to explicating Aquinas's thinking on the grounds of necessary propositions, I show how Aquinas thought that these propositions could remain true even after the creatures that they are about (and their forms) have perished.