aught we know, may be only in appearance similar; this is the main
question on which I would insist. The bread, which I formerly eat,
nourished me; that is, a body of such sensible qualities was, at that
time, endued with such secret powers: but does it follow, that other
bread must also nourish me at another time, and that like sensible
qualities must always be attended with like secret powers? The
consequence seems nowise necessary. At least, it must be acknowledged
that there is here a consequence drawn by the mind; that there is a
certain step taken; a process of thought, and an inference, which wants
to be explained. These two propositions are far from being the same, _I
have found that such an object has always been attended with such an
effect_, and _I foresee, that other objects, which are, in appearance,
similar, will be attended with similar effects_. I shall allow, if you
please, that the one proposition may justly be inferred from the other:
I know, in fact, that it always is inferred. But if you insist that the
inference is made by a chain of reasoning, I desire you to produce that
reasoning. The connexion between these propositions is not intuitive.
There is required a medium, which may enable the mind to draw such an
inference, if indeed it be drawn by reasoning and argument. What that
medium is, I must confess, passes my comprehension; and it is incumbent
on those to produce it, who assert that it really exists, and is the
origin of all our conclusions concerning matter of fact.

[6] The word, Power, is here used in a loose and popular sense.
The more accurate explication of it would give additional
evidence to this argument. See Sect. 7.

30. This negative argument must certainly, in process of time, become
altogether convincing, if many penetrating and able philosophers shall
turn their enquiries this way and no one be ever able to discover any