42. We may add force to these experiments by others of a different
kind, in considering the effects of contiguity as well as of
resemblance. It is certain that distance diminishes the force of every
idea, and that, upon our approach to any object, though it does not
discover itself to our senses it operates upon the mind with an
influence, which imitates an immediate impression. The thinking on any
object readily transports the mind to what is contiguous; but it is
only the actual presence of an object, that transports it with a
superior vivacity. When I am a few miles from home, whatever relates
to it touches me more nearly than when I am two hundred leagues
distant; though even at that distance the reflecting on anything in
the neighbourhood of my friends or family naturally produces an idea
of them. But as in this latter case, both the objects of the mind
are ideas; notwithstanding there is an easy transition between them;
that transition alone is not able to give a superior vivacity to any
of the ideas, for want of some immediate impression.*

  * "Naturane nobis, inquit, datum dicam, an errore quodam, ut, cum ea
loca videamus, in quibus memoria dignos viros acceperimus multum
esse versatos, magis moveamur, quam siquando eorum ipsorum aut facta
audiamus aut scriptum aliquod legamus? Velut ego nunc moveor. Venit
enim mihi Plato in mentem, quem accepimus primum hic disputare
solitum: cuius etiam illi hortuli propinqui non memoriam solum mihi
afferunt, sed ipsum videntur in conspectu meo hic ponere. Hic
Speusippus, hic Xenocrates, hic eius auditor Polemo; cuius ipsa illa
sessio fuit, quam videmus. Equidem etiam curiam nostram, Hostiliam
dico, non hanc novam, quae mihi minor esse videtur postquam est maior,
solebam intuens, Scipionem, Catonem, Laelium, nostrum vero in primis
avum cogitare. Tanta vis admonitionis est in locis; ut non sine
causa ex his memoriae deducta sit disciplina."

                                        Cicero, De finibus, Book V.

  43. No one can doubt but causation has the same influence as the
other two relations of resemblance and contiguity. Superstitious
people are fond of the reliques of saints and holy men, for the same
reason, that they seek after types or images, in order to enliven
their devotion, and give them a more intimate and strong conception of
those exemplary lives, which they desire to imitate. Now it is
evident, that one of the best reliques, which a devotee could procure,
would be the handywork of a saint; and if his cloaths and furniture
are ever to be considered in this light, it is because they were
once at his disposal, and were moved and affected by him; in which
respect they are to be considered as imperfect effects, and as
connected with him by a shorter chain of consequences than any of
those, by which we learn the reality of his existence.

  Suppose, that the son of a friend, who had been long dead or absent,
were presented to us; it is evident, that this object would
instantly revive its correlative idea, and recal to our thoughts all
past intimacies and familiarities, in more lively colours than they
would otherwise have appeared to us. This is another phaenomenon,
which seems to prove the principle above mentioned.

  44. We may observe, that, in these phaenomena, the belief of the
correlative object is always presupposed; without which the relation
could have no effect. The influence of the picture supposes, that we
believe our friend to have once existed. Continguity to home can never
excite our ideas of home, unless we believe that it really exists. Now
I assert, that this belief, where it reaches beyond the memory or
senses, is of a similar nature, and arises from similar causes, with
the transition of thought and vivacity of conception here explained.
When I throw a piece of dry wood into a fire, my mind is immediately
carried to conceive, that it augments, not extinguishes the flame.
This transition of thought from the cause to the effect proceeds not
from reason. It derives its origin altogether from custom and
experience. And as it first begins from an object, present to the
senses, it renders the idea or conception of flame more strong and
lively than any loose, floating reverie of the imagination. That
idea arises immediately. The thought moves instantly towards it, and
conveys to it all that force of conception, which is derived from
the impression present to the senses. When a sword is levelled at my
breast, does not the idea of wound and pain strike me more strongly,
than when a glass of wine is presented to me, even though by
accident this idea should occur after the appearance of the latter
object? But what is there in this whole matter to cause such a
strong conception, except only a present object and a customary
transition to the idea of another object, which we have been
accustomed to conjoin with the former? This is the whole operation
of the mind, in all our conclusions concerning matter of fact and
existence; and it is a satisfaction to find some analogies, by which
it may be explained. The transition from a present object does in
all cases give strength and solidity to the related idea.

  Here, then, is a kind of pre-established harmony between the
course of nature and the succession of our ideas; and though the
powers and forces, by which the former is governed, be wholly
unknown to us; yet our thoughts and conceptions have still, we find,
gone on in the same train with the other works of nature. Custom is
that principle, by which this correspondence has been effected; so
necessary to the subsistence of our species, and the regulation of our
conduct, in every circumstance and occurrence of human life. Had not
the presence of an object, instantly excited the idea of those
objects, commonly conjoined with it, all our knowledge must have
been limited to the narrow sphere of our memory and senses; and we
should never have been able to adjust means to ends, or employ our
natural powers, either to the producing of good, or avoiding of
evil. Those, who delight in the discovery and contemplation of final
causes, have here ample subject to employ their wonder and admiration.