Those who can find any argument in favour of the immaterial nature and independent powers of the soul in the sublime flights which it takes when emancipated from the intrusion of sensible objects must have finer dreams than I have. It would be well for this opinion if we could regularly forget the next morning the smart repartees, magnificent sentiments and profound remarks we so often dream we make. The singular significance which in sleep we attach to absolute nonsense seems to arise from the very impotence of our efforts, as we fancy that we can fly because we cannot move at all. In sleep, indeed, the forms of imagination assume the appearance of reality, but this advantage they seem to owe chiefly to what Hobbes calls the silence of sense. That sleep, however, consists wholly in this silence of sense (not affecting the mind itself) is so far from being true, that it is not even necessary to it. Persons who walk in their sleep, as I know from experience, get out of bed with their eyes open, see and feel the objects about them, open the window, and leisurely survey the opposite trees and houses, long before they recollect where they are, or before the fresh air and the regular succession of known objects dispel the drowsy phantoms of the night. The only essential difference be

tween our sleeping and waking thoughts I believe is, that in sleep the comprehensive faculty flags and droops; so that being unable to consider many things at once or to retain a succession of ideas in mind, we confound things together, and pass from one object to another without order or connexion, any single circumstance in which they agree being sufficient to make us associate them together or substitute one for the other. Our thoughts are, as it were, disentangled from the circumstances and consequences which at other times clog their motions: they are let loose, and left at liberty to wander in any direction that chance presents. The greatest singularity observable in dreams is the faculty of holding a dialogue with ourselves, as if we were really and effectually two persons. We make a remark, and then expect the answer, which we are to give ourselves, with the same gravity of attention, and hear it with the same surprise as if it were really spoken by another person. We are played upon by puppets of our own moving. We are staggered in an argument by an unforeseen objection, or alarmed at a sudden piece of information of which we have no apprehension till it seems to proceed from the mouth of some one with whom we fancy ourselves conversing. We have in fact no idea

of what the question will be that we put to ourselves till the moment of its birth.

Mr Locke in treating of our sensations as effects of the impressions of the qualities of things, distinguishes these qualities according to the usual opinion into primary and secondary. The former he considers as really and in themselves the same as they appear to our senses: the other as merely the effects produced by certain objects on the mind and not existing out of it. As this question forms one of the commonplaces of metaphysical inquiry, I shall give some account of it in his own words.

"The qualities that are in bodies, rightly considered, are of three sorts.

"First, The bulk, figure, number, situation, and motion or rest of their solid parts; these are in them whether we perceive them or no: and we have by these an idea of the thing as it is in itself: these I call primary qualities.

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Secondly, The power that is in any body by reason of its insensible primary qualities to operate after a peculiar manner on any of our senses, and thereby produce in us the different ideas of several colours, sounds, smells, tastes, &c. These are usually called sensible qualities.

"Thirdly, The power that is in any body, by

reason of the particular constitution of its primary qualities, to make such a change in the bulk, figure, texture, and motion of another body, as to make it operate on our senses differently from what it did before. Thus the sun has a power to make wax white, and fire to make lead fluid. These are usually called powers.

"The first of these, as has been said, I think, may be properly called, real, original, or primary qualities, because they are in the things themselves, whether they are perceived or no: and upon their different modifications it is that the secondary qualities depend. The other two are only powers to act differently upon other things, which powers result from the different modifications of those primary qualities.

"But though these two latter sorts of qualities are powers barely, and nothing but powers, relating to several other bodies, and resulting from the different modifications of the original qualities, yet they are generally thought otherwise of. For the second sort, viz., the powers to produce several ideas in us by our senses, are looked upon as real qualities in the things thus affecting us: but the third sort are called and esteemed barely powers. For example, the ideas of heat or light, which we receive

by our eye or touch from the sun are commonly thought real qualities, existing in the sun, and something more than mere powers in it. But when we consider the sun in reference to wax which it melts or blanches, we look on the whiteness and softness produced in the wax, not as qualities in the sun, but effects produced by powers in it: whereas, if rightly considered, these qualities of light and warmth, which are perceptions in me when I am warmed or enlightened by the sun, are no otherwise in the sun than the changes made in the wax, when it is blanched or melted, are in

the sun. They are all of them equally powers in the sun, depending on its primary qualities: whereby it is enabled in the one case so to alter the bulk, figure, texture, or motion of some of the insensible parts of my eyes or hands, as thereby to produce in me the idea of light or heat; and in the other, it is able so to alter the bulk, figure, texture, or motion of the insensible parts of the wax, as to make them fit to produce in me the distinct ideas of white and fluid. The reason why the one are ordinarily taken for real qualities, and the other only for bare powers, seems to be, because the ideas we have of distinct colours, sounds, &c., containing nothing at all in them of bulk, figure, or motion,