that it will not be difficult, upon these suppositions, to find other
operations of the mind analogous to it, and to trace up these phenomena
to principles still more general.

41. We have already observed that nature has established connexions
among particular ideas, and that no sooner one idea occurs to our
thoughts than it introduces its correlative, and carries our attention
towards it, by a gentle and insensible movement. These principles of
connexion or association we have reduced to three, namely,
_Resemblance_, _Contiguity_ and _Causation_; which are the only bonds
that unite our thoughts together, and beget that regular train of
reflection or discourse, which, in a greater or less degree, takes place
among all mankind. Now here arises a question, on which the solution of
the present difficulty will depend. Does it happen, in all these
relations, that, when one of the objects is presented to the senses or
memory, the mind is not only carried to the conception of the
correlative, but reaches a steadier and stronger conception of it than
what otherwise it would have been able to attain? This seems to be the
case with that belief which arises from the relation of cause and
effect. And if the case be the same with the other relations or
principles of associations, this may be established as a general law,
which takes place in all the operations of the mind.

We may, therefore, observe, as the first experiment to our present
purpose, that, upon the appearance of the picture of an absent friend,
our idea of him is evidently enlivened by the _resemblance_, and that
every passion, which that idea occasions, whether of joy or sorrow,
acquires new force and vigour. In producing this effect, there concur
both a relation and a present impression. Where the picture bears him no
resemblance, at least was not intended for him, it never so much as