persons who have seen such dreams, those, for example, who believe

themselves to be mentally arranging a given list of subjects according

to the mnemonic rule. They frequently find themselves engaged in

something else besides the dream, viz. in setting a phantasm which

they envisage into its mnemonic position. Hence it is plain that not

every 'phantasm' in sleep is a mere dream-image, and that the

further thinking which we perform then is due to an exercise of the

faculty of opinion.

So much at least is plain on all these points, viz. that the faculty

by which, in waking hours, we are subject to illusion when affected by

disease, is identical with that which produces illusory effects in

sleep. So, even when persons are in excellent health, and know the

facts of the case perfectly well, the sun, nevertheless, appears to

them to be only a foot wide. Now, whether the presentative faculty

of the soul be identical with, or different from, the faculty of

sense-perception, in either case the illusion does not occur without

our actually seeing or [otherwise] perceiving something. Even to see

wrongly or to hear wrongly can happen only to one who sees or hears

something real, though not exactly what he supposes. But we have

assumed that in sleep one neither sees, nor hears, nor exercises any

sense whatever. Perhaps we may regard it as true that the dreamer sees

nothing, yet as false that his faculty of sense-perception is

unaffected, the fact being that the sense of seeing and the other

senses may possibly be then in a certain way affected, while each of

these affections, as duly as when he is awake, gives its impulse in

a certain manner to his [primary] faculty of sense, though not in

precisely the same manner as when he is awake. Sometimes, too, opinion

says [to dreamers] just as to those who are awake, that the object

seen is an illusion; at other times it is inhibited, and becomes a

mere follower of the phantasm.

It is plain therefore that this affection, which we name 'dreaming',

is no mere exercise of opinion or intelligence, but yet is not an