kind are judiciously collected and compared, we may hope to establish on them a science which will not be inferior in certainty, and will be much superior in utility, to any other of human comprehension. [1] Mr Locke, my Lord Shaftsbury, Dr Mandeville, Mr Hutchinson, Dr Butler, &c. BOOK I. OF THE UNDERSTANDING. PART I. OF IDEAS, THEIR ORIGIN, COMPOSITION, CONNEXION, AND ABSTRACTION. SECTION I. OF THE ORIGIN OF OUR IDEAS. All the perceptions of the human mind resolve themselves into two distinct kinds, which I shall call _impressions_ and _ideas_. The difference betwixt these consists in the degrees of force and liveliness, with which they strike upon the mind, and make their way into our thought or consciousness. Those perceptions which enter with most force and violence, we may name _impressions_; and, under this name, I comprehend all our sensations, passions, and emotions, as they make their first appearance in the soul. By _ideas_, I mean the faint images of these in thinking and reasoning; such as, for instance, are all the perceptions excited by the present discourse, excepting only those which arise from the sight and touch, and excepting the immediate pleasure or uneasiness it may occasion. I believe it will not be very necessary to employ many Words, in explaining this distinction. Every one of himself will readily perceive the difference betwixt feeling and thinking. The common degrees of these are easily distinguished; though it is not impossible but, in particular instances, they may very nearly approach to each other. Thus, in sleep, in a fever, in madness, or in any very violent emotions of soul, our ideas may approach to our impressions: as, on the other hand, it sometimes happens, that our impressions are so faint and low, that we cannot distinguish them from our ideas. But, notwithstanding this near resemblance in a few instances, they are in general so very different, that no one can make a scruple to rank them under distinct heads, and assign to each a peculiar name to mark the difference.[1] There is another division of our perceptions, which it will be convenient to observe, and which extends itself both to our impressions and ideas. This division is into _simple_ and _complex_. Simple perceptions, or impressions and ideas, are such as admit of no distinction nor separation. The complex are the contrary to these, and may be distinguished into parts. Though a particular colour, taste and smell, are qualities all united together in this apple, 'tis easy to perceive they are not the same, but are at least distinguishable from each other.