CHAPTER III.
THE ORIGIN OF THE IMPRESSIONS.
Admitting that the sensations, the feelings of pleasure and pain, and those of relation, are the primary irresolvable states of consciousness, two further lines of investigation present themselves.

The one leads us to seek the origin of these "impressions;" the other, to inquire into the nature of the steps by which they become metamorphosed into those compound states of consciousness, which so largely enter into our ordinary trains of thought.
With respect to the origin of impressions of sensation, Hume is not quite consistent with himself.

In one place (I.p.

117) he says, that it is impossible to decide "whether they arise immediately from the object, or are produced by the creative power of the mind, or are derived from the Author of our being," thereby implying that realism and idealism are equally probable hypotheses.

But, in fact, after the demonstration by Descartes, that the immediate antecedents of sensations are changes in the nervous system, with which our feelings have no sort of resemblance, the hypothesis that sensations "arise immediately from the object" was out of court; and that Hume fully admitted the Cartesian doctrine is apparent when he says (I.p.