already so firmly established, as to admit of no farther doubt; at least,
till we have more fully examined the present difficulty.

We must, therefore, proceed like those, who being in search of any thing,
that lies concealed from them, and not finding it in the place they
expected, beat about all the neighbouring fields, without any certain
view or design, in hopes their good fortune will at last guide them to
what they search for. It is necessary for us to leave the direct survey of
this question concerning the nature of that necessary connexion, which
enters into our idea of cause and effect; and endeavour to find some
other questions, the examination of which will perhaps afford a hint,
that may serve to clear up the present difficulty. Of these questions
there occur two, which I shall proceed to examine, viz.

First, For what reason we pronounce it necessary, that every thing whose
existence has a beginning, should also have a cause.

Secondly, Why we conclude, that such particular causes must necessarily
have such particular effects; and what is the nature of that inference we
draw from the one to the other, and of the belief we repose in it?

I shall only observe before I proceed any farther, that though the ideas
of cause and effect be derived from the impressions of reflection as well
as from those of sensation, yet for brevity's sake, I commonly mention
only the latter as the origin of these ideas; though I desire that
whatever I say of them may also extend to the former. Passions are
connected with their objects and with one another; no less than external
bodies are connected together. The same relation, then, of cause and
effect, which belongs to one, must be common to all of them.