Now Theaetetus remembers hearing someone say that knowledge is true judgment with an account (logos). According to his source, things that lacked an account were not knowable. Socrates offers a “dream” to help clarify the proposed definition. “I think I have heard people saying that the first components, like elements (stoicheia), from which we and everything else are composed, lack an account.” This, according to ancient commentators, is the first extant use of the term stoicheion as ‘element.’[56] This suggests the analogy to letters of the alphabet (also called stoicheia), which can be woven together (sumplekein) into the fabric of an account. We are reminded of what Plato said in the Cratylus about composing (written) words from letters, and sentences from words.[57]
Theaetetus and Plato seem to have in mind not only the construction of linguistic compositions, but the composition of physical objects as well. Thus, we could suppose that a compound like wood was composed of (in modern terms) carbon, hydrogen, and oxygen or (in ancient terms) of earth, water, air, and fire, in a certain ratio. We could point out the elements but we could not “explain” them by analyzing them. If the elements are simple, then they just are what they are, like letters of the alphabet each representing a given sound. On the other hand, we could explain or give an account of the compound by analyzing it into its components in a given order or structure.
But Socrates points out that a whole must be more than the sum of its parts. If so, it must have a single form (idea) of its own and not be reducible to its parts.[58] This conclusion seems to undermine the claim that knowledge is true judgment with an account.
Socrates suggests considering the different meanings ‘account’ (logos) might have. In fact the Greek term has a long list of definitions in a lexicon. Socrates offers three relevant possibilities. First, it might mean the verbal representation of a person’s thought. Second, it might mean the analysis of a complex into its components, the interpretation that has guided the recent discussion between Socrates and Theaetetus. Third, it might signify a distinguishing mark for identifying something or someone. The first meaning is too general to be useful. The second would reduce the whole to a list of parts. The third seems to presuppose knowledge that is contained in the true judgment: to distinguish Theaetetus from other people, I already have to know who Theaetetus is. This case suggests that Plato is thinking of knowledge by acquaintance rather than knowledge by description (to use a modern distinction). He has not, unfortunately, made any investigation into kinds of knowledge or ways of knowing, much less resolved them one by one.
In any case, we come to the end of a long and complex inquiry into knowledge, without attaining a workable definition or an adequate understanding. The present dialogue from the end of Plato’s middle period is much like many Socratic dialogues of his early period, an inquiry which fails to achieve its goal of elucidating some philosophical concept.
[56] Eudemus from Simplicius On Physics 7.13.*
[57] Plato Cratylus 424b-425a.
[58] Plato Theaetetus 204a.