ing for ever present with us; when
we consider a stedfast object at five-a-clock, and regard the same at
six; we are apt to apply to it that idea in the same manner as if every
moment were distinguished by a different position, or an alteration
of the object. The first and second appearances of the object, being
compared with the succession of our perceptions, seem equally removed as
if the object had really changed. To which we may add, what experience
shews us, that the object was susceptible of such a number of changes
betwixt these appearances; as also that the unchangeable or rather
fictitious duration has the same effect upon every quality, by
encreasing or diminishing it, as that succession, which is obvious to
the senses. From these three relations we are apt to confound our ideas,
and imagine we can form the idea of a time and duration, without any
change or succession.

SECT. VI. OF THE IDEA OF EXISTENCE, AND OF EXTERNAL EXISTENCE.

It may not be amiss, before we leave this subject, to explain the ideas
of existence and of external existence; which have their difficulties,
as well as the ideas of space and time. By this means we shall be the
better prepared for the examination of knowledge and probability, when
we understand perfectly all those particular ideas, which may enter into
our reasoning.

There is no impression nor idea of any kind, of which we have any
consciousness or memory, that is not conceived as existent; and it
is evident, that from this consciousness the most perfect idea and
assurance of being is derived. From hence we may form a dilemma, the
most clear and conclusive that can be imagined, viz. that since we never
remember any idea or impression without attributing existence to it,
the idea of existence must either be derived from a distinct impression,
conjoined with every perception or object of our thought, or must be the
very same with the idea of the perception or object.

As this dilemma is an evident consequence of the principle, that every
idea arises from a similar impression, so our decision betwixt the
propositions of the dilemma is no more doubtful go far from there being
any distinct impression, attending every impression and every idea,
that I do not think there are any two distinct impressions, which are
inseparably conjoined. Though certain sensations may at one time be
united, we quickly find they admit of a separation, and may be presented
apart. And thus, thou