Truth and Existence
The concepts of truth and existence form a natural pair. They are both highly general abstract concepts. They have both been suspected of being pseudo-properties, expressed by logically misleading predicates. They have both been declared redundant, adding nothing to their bearers: calling a proposition true amounts to no more than affirming the proposition, and ascribing existence to a denoted object does nothing more than bring out what is presupposed in denoting that object. Also, truth pairs with falsehood in the way existence pairs with non-existence: truth and existence are positive attributes, while falsehood and non-existence are types of lack. Truth and existence are deemed good, while falsehood and non-existence are deemed bad: we aim to assert what is true, as we aim to refer to what exists. If we fail in these aims, we do something amiss. Finally, it has often been supposed that truth and existence are fundamental and indefinable concepts, with the associated properties ontologically primitive (and vaguely “queer”). Neither property can be perceived via the senses, and neither plays a causal role in how the world works. They both seem non-empirical, non-natural, and oddly diaphanous.
This raises the question of whether truth and existence are related in any way: do they perhaps enter into each other’s essential nature? If there is any interesting connection, it will not be simple—not a matter of defining one in terms of the other by substitution. Thus it is hopeless to suggest that ”p is true” means “p exists”, since a proposition can exist without being true (though the former follows from the latter). And it is equally hopeless to equate “a exists” with “a is true”, since objects cannot be true (or false). Clearly truth and existence are not the same property. But the connection might be less direct—one concept might be linked to the other in combination with other concepts. Thus consider: “A proposition is true if and only if it designates an existing state of affairs”. That sounds very much on the right lines (Tarski mentions it as a possible definition of truth). Note that we need to include “existing” here because a proposition might designate a possible state of affairs that does not exist (is not actual): the possible state of affairs of snow being yellow does not exist. The world is the totality of existing states of affairs. Given that we are happy with states of affairs, and with applying the concept of existence to them, this seems like a perfectly worthy definition of truth; and it contains the concept of existence essentially. Thus truth is conceptually linked to existence.
What about the other way round—is existence linked to truth? The following sounds right: if a exists, then we can make true statements about a. If a does not exist, then we cannot make true statements about a—we can make only false statements or statements that are neither true nor false. Existence is a necessary condition for true predication: we cannot speak truly of something that does not exist. Someone might object that this principle is false for fictional objects, since we can say truly that Sherlock Holmes is a detective. Maybe or maybe not, but we can easily strengthen the principle to say that existence is a necessary condition of literal or factual truth. Thus the concept of existence entails a consequence concerning truth—existence is what makes truth possible. In a world with no existence there is no truth. If we are feeling ambitious, we might even try to define existence this way: an object exists if and only if there are true statements about it. This would be the analogue of defining truth in terms of existing states of affairs. But we do not need to go that far in order to recognize a non-trivial conceptual link—a kind of mutual conceptual dependence. Grasp of the concept of truth involves grasp of the concept of existence and vice versa: one concept feeds into the other.
Granted these links, the similarities between truth and existence fall naturally into place: they are concepts that presuppose each other. Truth is all about the existence of states of affairs, and existence is all about the stating of truths. Truth is a certain kind of existence, and existence is the basis of truth. We have the word “true” so that we can describe existing of states of affairs, and we have the word “exists” so that we can describe what makes truth possible. We could get along without these short words, using only the longwinded formulations, saying things like, “Your statement designates an existing state of affairs” and “a meets the condition for allowing true statements about a”. What is notable about these definitions is that each concept incorporates the other concept essentially. Thus truth and existence are natural conceptual partners: they point towards each other.