Höhlengleichnis
Instead, Socrates continues, knowledge is to be found in "... that region in which truth and real being brightly shine..." (508d) This is the intelligible illuminated by the highest idea, that of goodness. Since truth and being find their source in this highest idea, only the souls that are illumined by this source can be said to possess knowledge, whereas those souls which turn away are "...mingled with darkness...". This subject is later vividly illustrated in the Allegory of the Cave (514a–520a), where prisoners bound in a dark cave since childhood are examples of these souls turned away from illumination.