gn 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