also that any habit should ever
exceed that degree of regularity. Any degree, therefore, of regularity
in our perceptions, can never be a foundation for us to infer a greater
degree of regularity in some objects, which are not perceived; since
this supposes a contradiction, viz. a habit acquired by what was never
present to the mind. But it is evident, that whenever we infer the
continued existence of the objects of sense from their coherence, and
the frequency of their union, it is in order to bestow on the objects
a greater regularity than what is observed in our mere perceptions. We
remark a connexion betwixt two kinds of objects in their past appearance
to the senses, but are not able to observe this connexion to be
perfectly constant, since the turning about of our head or the shutting
of our eyes is able to break it. What then do we suppose in this
case, but that these objects still continue their usual connexion,
notwithstanding their apparent interruption, and that the irregular
appearances are joined by something, of which we are insensible? But as
all reasoning concerning matters of fact arises only from custom, and
custom can only be the effect of repeated perceptions, the extending of
custom and reasoning beyond the perceptions can never be the direct and
natural effect of the constant repetition and connexion, but must arise
from the co-operation of some other principles.

I have already observed [Part II, Sect. 4.], in examining the foundation
of mathematics, that the imagination, when set into any train of
thinking, is apt to continue, even when its object fails it, and like a
galley put in motion by the oars, carries on its course without any new
impulse. This I have assigned for the reason, why, after considering
several loose standards of equality, and correcting them by each other,
we proceed to imagine so correct and exact a standard of that relation,
as is not liable to the least error or variation. The same principle
makes us easily entertain this opinion of the continued existence
of body. Objects have a certain coherence even as they appear to our
senses; but this coherence is much greater and more uniform, if we
suppose the object.% to have a continued existence; and as the mind is
once in the train of observing an uniformity among objects, it naturally
continues, till it renders the uniformity as compleat as possible.
The simple supposition of their continued existence suffices for this
purpose