‘Again, imagination being only of those things which have been formerly perceived by sense, either all at once, or by parts at several times, the former (which is the imagining the whole object as it was presented to the sense) is _simple imagination_; as when one imagineth a man or horse which he hath seen before. The other is _compounded_, as when from the sight of a man at one time, and of a horse at another, we conceive in our mind a centaur. So when a man compoundeth the image of his own person with the image of the actions of another man; as when a man conceives himself a Hercules or an Alexander (which happeneth often to them which are much taken with the reading of Romaunts) it is a compound imagination, and properly but a fiction of the mind. ‘There be also other imaginations that rise in man, (though waking) from the great impression made in sense: as from gazing upon the sun, the impression leaves an image of the sun before our eyes a long time after; and from being long and vehemently attent upon geometrical figures, a man shall in the dark (though awake) have the image of lines and angles before his eyes: which kind of fancy hath no particular name; as being a thing that doth not commonly fall into men’s discourse. ‘The imaginations of them that sleep are those we call dreams: and these also (as all other imaginations) have been before, either totally or by parcels in the sense, and because the brain and nerves, which are the necessary organs of sense, are so benumbed in sleep, as not easily to be moved by the action of external objects, there can happen in sleep no imagination; and therefore no dream but what proceeds from the agitation of the inward parts of man’s body; which inward parts, for the connexion they have with the brain and other organs, when they be distempered, do keep the same in motion; whereby the imaginations there formerly made, appear as if a man were waking; saving that the organs of sense being now benumbed, so as there is no new object, which can master and obscure them with a more vigorous impression, a dream must needs be more clear in this silence of sense, than are our waking thoughts. And hence it cometh to pass, that it is a hard matter, and by many thought impossible, to distinguish exactly between sense and dreaming. For my part, when I consider that in dreams I do not often, nor constantly think of the same persons, places, subjects, and actions that I do waking; nor remember so long a train of coherent thoughts dreaming, as at other times; and because waking I often observe the absurdity of dreams, but never dream of the absurdities of my waking thoughts,—I am well satisfied, that being awake, I know I dream not; though when I dream, I think myself awake.’—_Leviathan_, pp. 4, 5, 6. The concluding paragraph of this Chapter is remarkable.