Abstract

In Republic VI, Plato’s Socrates attempts to explain the nature of human understanding by means of a simile of a line divided into four unequal segments. Socrates directs Glaucon to accept as names for the four states ‘rational knowledge’ for the highest, ‘understanding’ for the second, ‘belief’ for the third, and for the last, ‘perception of images.’ He then directs Glaucon to arrange the four states in a proportion, ‘considering that they participate in saphēneia in the same degree to which their objects participate in reality.’ Although saphêneia here is usually translated as ‘clarity, ’I argue that neither ‘clarity’ nor ‘truth’ nor ‘knowledge’ provides an entirely satisfactory translation. Rather, in this context saphêneia is best understood as ‘a full, accurate, and sure awareness.’ Plato’s simile, properly understood, provides not only an explanation of his rationalist theory of knowledge but also a coherent line of argument in support of that theory.