This famous quote from our forty-second President is a tell-tale sign. Our President was a Rhodes Scholar at Oxford and at Oxford they take the definition of the word “is” very seriously. Witness the article “Plato and the Copula: Sophist 251 – 259” by J. L. Ackrill, “Fellow, Tutor, and Lecturer in Philosophy, Brasemose College, Oxdord.” Ackrill credits Plato with “the recognition of the ambiguity of ϵστίν as used on the one hand in statements of identity and on the other hand in attributive statements.”
Had you ever heard of the word “copula”? Kind of makes one think of the affair which caused our forty-second President to come up with our title quote. Well maybe you are one of those “late-learners” in the words of Plato’s Sophist 251, “whose learning has come to them late in life; for example, it is easy enough for anyone to grasp the notion that the many cannot possibly be one, nor the one many, and so, apparently, they take pleasure in saying that we must not call a man good, but must call the good good, and a man man. I fancy, Theaetetus, you often run across people who take such matters seriously; sometimes they are elderly men whose poverty of intellect makes them admire such quibbles, and who think this is a perfect mine of wisdom they have discovered.” (H.N. Fowler translation from the Loeb Classical Library)
While Ackrill points out that there are at least three meanings for the word “is”, he credits Plato with distinguishing two: 1) as the copula, which connects two named concepts and 2) as the indicator of identity. The third meaning would be the existential usage. It is in confusing the first two uses with the third, that Plato’s Eleatic Stranger in the Sophist points out the errors in the ways of his “father”, Parmenides.