What is Truth?

by Mortimer J. Adler, Ph.D.

Dear Dr. Adler,

I find it hard to define what truth is. Some of my friends say that truth is what most people think is so. But that does not make sense to me, because sometimes the majority is wrong. Even what everyone thinks is so may not be the truth. There must be some better definition of truth. What is it?

A. N.

Dear A. N.,

You are quite right to feel dissatisfied. Your friends did not arrive at a definition of truth, but at one of the signs of truth. In certain cases the fact that the majority holds something to be true is an indication that it is probably true. But this is only one of the signs of truth, and by no means the best one. And it does not answer your question or Pilate’s — “What is truth?”

It may help you to understand the nature of truth to consider what is involved in telling a lie. If a man tells a woman “I love you” when he does not, he is telling a lie. When a child who has raided the cookie jar tells his mother “I didn’t,” he is lying. Lying consists in saying the opposite of what you know, think, or feel. It is distinct from honest error, such as that of the umpire who calls a man “out” when he is “safe,” or vice versa.

Josiah Royce, a great American philosopher at the beginning of this century, defined a liar as a man who willfully misplaces his ontological predicates; that is, a man who says “is” when he means “is not,” or “is not” when he means “is.” Royce’s definition of a liar leads us quickly to the most famous of all philosophical definitions of truth. It was given by Plato and Aristotle almost twenty-five centuries ago; it has been repeated in various ways ever since, and seldom been improved upon.

Plato and Aristotle say that the opinions we hold are true when they assert that that which is, is, or that that which is not, is not; and that our opinions are false when they assert that that which is, is not, or that that which is not, is.

When the “is” in a statement we make agrees with the way things are, then our statement is true, and its truth consists in its corresponding to the existent facts of nature and reality. When we think that something exists or has happened which does not exist or did not happen, then we are mistaken and what we think is false.

So, as you see, truth is very easy to define, and the definition is not very hard to understand. Perhaps impatient Pilate would have waited for the answer if he had known that it could be given so briefly. But maybe he was thinking of another question, “How can we tell whether a statement is true or false?” This, by the way, is the question you and your friends ended up by answering.

To this question there are three main types of answer. The first insists that some statements are self-evidently true, such as, “The whole is greater than the part.” Such statements reveal their truth to us directly by the fact that we find it impossible to think the opposite of them. When we understand what a whole is and what a part is, we cannot think that a part is greater than the whole to which it belongs. That is how we know immediately the truth of the statement that the whole is greater than any of its parts.

Another type of answer says that the truth of statements can be tested by our experience or observations. If a man says that it did not rain in Chicago a single day last month, we can check the truth of his statement by looking up the official weather records. Or we can stick a foot into a swimming pool to see if the water is as warm as a friend says it is. Similarly, a scientific generalization is considered true only as long as no contrary facts are observed.

The third type of answer has to do with statements that are neither self-evidently true nor capable of being checked by direct appeal to observed facts. It may be a question of a person’s character, what type of product is most desirable for certain purposes, or whether the favorite will win the next race. Here it is permissible to count noses and to find the consensus of a group of people or of the experts. That an opinion is held by a majority can be taken as a sign that it has some probability of being true.

This third answer was the one your friend arrived at. But the fact that it expressed the consensus of the group does not make it the right answer to the question, “What is truth?” Nor does it give the full answer to the question, “How can we tell whether a statement is true? Defining truth is easy; knowing whether a particular statement is true is much harder; and pursuing the truth is most difficult of all.

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