But as we here not only feign but believe this continued existence, the question is, from whence arises such a belief; and this question leads us to the fourth member of this system.  It has been proved already, that belief in general consists in nothing, but the vivacity of an idea; and that an idea may acquire this vivacity by its relation to some present impression.  Impressions are naturally the most vivid perceptions of the mind; and this quality is in part conveyed by the relation to every connected idea.  The relation causes a smooth passage from the impression to the idea, and even gives a propensity to that passage.  The mind falls so easily from the one perception to the other, that it scarce perceives the change, but retains in the second a considerable share of the vivacity of the first.  It is excited by the lively impression; and this vivacity is conveyed to the related idea, without any great diminution in the passage, by reason of the smooth transition and the propensity of the imagination.

But suppose, that this propensity arises from some other principle, besides that of relation; it is evident it must still have the same effect, and convey the vivacity from the impression to the idea.  Now this is exactly the present case.  Our memory presents us with a vast number of instances of perceptions perfectly resembling each other, that return at different distances of time, and after considerable interruptions.  This resemblance gives us a propension to consider these interrupted perceptions as the same; and also a propension to connect them by a continued existence, in order to justify this identity, and avoid the contradiction, in which the interrupted appearance of these perceptions seems necessarily to involve us.  Here then we have a propensity to feign the continued existence of all sensible objects; and as this propensity arises from some lively impressions of the memory, it bestows a vivacity on that fiction:  or in other words, makes us believe the continued existence of body.  If sometimes we ascribe a continued existence to objects, which are perfectly new to us, and of whose constancy and coherence we have no experience, it is because the manner, in which they present themselves to our senses, resembles that of constant and coherent objects; and this resemblance is a source of reasoning and analogy, and leads us to attribute the same qualities to similar objects.

I believe an intelligent reader will find less difficulty to assent to this system, than to comprehend it fully and distinctly, and will allow, after a little reflection, that every part carries its own proof along with it.  It is indeed evident, that as the vulgar suppose their perceptions to be their only objects, and at the same time believe the continued existence of matter, we must account for the origin of the belief upon that supposition.  Now upon that supposition, it is a false opinion that any of our objects, or perceptions, are identically the same after an interruption; and