Plato describes the existence of opinions in the soul as follows. The opinions formed by the operations of memory and perception are as it were written in the book of the soul. They can be expressed in spoken language and are true or false. These opinions are also illustrated in the same book by pictures formed by imagination. When something pertain- ing to perceptions is believed, there is also a picture in the soul which shows the perceptual content as it was revealed to the subject (39a–40d)