In Process and Reality, Alfred North Whitehead characterized the European philosophical tradition as consisting in a series of footnotes to Plato. In the Philosophical Investigations, Wittgenstein declares that the concept of an object, which he used in the Tractatus, is modeled on the concept of a primary element, which Plato used in the Theaetetus, where Plato argued that there must be primary elements which are simple and therefore nondescribable but only nameable because the essence of speech is the composition of names; names become descriptive language by being compounded together. Professor Wolniewicz has argued today that Wittgenstein's footnote to Plato is really an Aristotelian footnote.