done to arrive
at my chamber, unless the stairs I remember be not annihilated by my
absence. But this is not all. I receive a letter, which upon, opening
it I perceive by the hand-writing and subscription to have come from a
friend, who says he is two hundred leagues distant. It is evident I can
never account for this phenomenon, conformable to my experience in other
instances, without spreading out in my mind the whole sea and continent
between us, and supposing the effects and continued existence of posts
and ferries, according to my Memory and observation. To consider
these phaenomena of the porter and letter in a certain light, they are
contradictions to common experience, and may be regarded as objections
to those maxims, which we form concerning the connexions of causes and
effects. I am accustomed to hear such a sound, and see such an object in
motion at the same time. I have not received in this particular instance
both these perceptions. These observations are contrary, unless I
suppose that the door still remains, and that it was opened without
my perceiving it: And this supposition, which was at first entirely
arbitrary and hypothetical, acquires a force and evidence by its being
the only one, upon which I can reconcile these contradictions. There
is scarce a moment of my life, wherein there is not a similar instance
presented to me, and I have not occasion to suppose the continued
existence of objects, in order to connect their past and present
appearances, and give them such an union with each other, as I have
found by experience to be suitable to their particular natures and
circumstances. Here then I am naturally led to regard the world, as
something real and durable, and as preserving its existence, even when
it is no longer present to my perception.

But though this conclusion from the coherence of appearances may seem to
be of the same nature with our reasonings concerning causes and effects;
as being derived from custom, and regulated by past experience; we
shall find upon examination, that they are at the bottom considerably
different from each other, and that this inference arises from the
understanding, and from custom in an indirect and oblique manner. For
it will readily be allowed, that since nothing is ever really present to
the mind, besides its own perceptions, it is not only impossible,
that any habit should ever be acquired otherwise than by the regular
succession of these perceptions, but