I should now consider the principal tribes comprehended under the general name of moral evidence; but, that everydifficulty may be removed, which might retard our progress in the proposed discussion, it will be necessary, in the first place, to explore more accurately those sources in our nature which give being to experience, and consequently to all those attainments, moral and intellectual, that are derived from it. These sources are two, sense and memory. The senses, both external and internal, are the original inlets of perception. They inform the mind of the facts, which in the present instant are situated within the sphere of their activity, and no sooner discharge their office in any particular instance than the articles of information exhibited by them are devolved on the memory. Remembrance instantly succeeds sensation, insomuch that the memory becomes the sole repository of the knowledge received from sense; knowledge which, without this repository, would be as instantaneously lost as it is gotten, and could be of no service to the mind. Our sensations would be no better than the fleeting pictures of a moving object on a camera obscura, which leave not the least vestige behind them. Memory, therefore, is the only original voucher extant of those past realities for which we had once the evidence of sense. Her ideas are, as it were, the prints that have been left by sensible impressions. But from these two faculties, considered in themselves, there results to us the knowledge only of individual facts,and only of such facts as either heretofore have come, or at present do come, under the notice of our senses.
Now, in order to render this knowledge useful to us, in discovering the nature of things, and in regulating our conduct, a further process of the mind is necessary, which deserves to be carefully attended to, and may be thus illustrated. I have observed a stone fall to the ground when nothing intervened to impede its motion. This single fact produces little or no effect on the mind beyond a bare remembrance. At another time, I observe the fall of a tile, at another of an apple, and so of almost every kind of body in the like situation. Thus my senses first, and then my memory, furnish me with numerous examples, which, though different in every other particular, are similar in this, that they present a body moving downwards,till obstructed either by the ground or by some intervenient object. Hence my first notion of gravitation. For with regard to the similar circumstances of different facts, as by the repetition such circumstances are more deeply imprinted, the mind acquires a habit of retaining them, omitting those circumstances peculiar to each wherein their differences consist. Hence, if objects of any kind, in a particular manner circumstanced, are remembered to have been usually, and still more if uniformly, succeeded by certain particular consequences, the idea of the former, in the supposed circumstance introduced into the mind, immediately associates the idea of the latter;and if the object itself, so circumstanced, be presented to the senses, the mind instantly anticipates the appearance of the customary consequence. This holds also inversely. The retention and association above explained are called Experience. The anticipation is in effect no other than a particular conclusion from that experience. Here we may remark by the way, that though memory gives birth to experience, which results from the comparison of facts remembered, the experience or habitual association remains, when the individual facts on which it is founded are all forgotten. I know from an experience which excludes all doubt, the power of fire in melting silver, and yet may not be able at present to recollect a particular instance in which I have seen this effect produced, or even in which I have had the fact attested by a credible witness.
Some will perhaps object that the account now given makes our experimental reasoning look like a sort of mechanism, necessarily resulting from the very constitution of the mind. I acknowledge the justness of the remark, but do not think that it ought to be regarded as an objection. It is plain that our reasoning in this way, if you please to call it so, is very early, and precedes all reflection on our faculties, and the manner of applying them. Those who attend to the progress of human nature through its different stages, and through childhood in particular, will observe that children make great acquisitions in knowledge from experience long before they attain the use of speech. The beasts also, in their sphere, improve by experience, which hath in them just the same foundations of sense and memory as in us, and hath, besides, a similar influence on their actions. It is precisely in the same manner, and with the same success, that you might train a dog, or accustom a child to expect food on your calling to him in one tone of voice, and to dread your resentment when you use another. The brutes have evidently the rudiments of this species of rationality, which extends as far in them as the immediate purposes of self-preservation require, and which, whether you call it reason or instinct, they both acquire and use in the same manner as we do. That it reaches no further in them, seems to arise from an original incapacity of classing, and (if I may use the expression) generalizing their perceptions; an exercise which to us very quickly becomes familiar, and is what chiefly fits us for the use of language. Indeed, in the extent of this capacity, as much, perhaps, as in any thing, lies also the principal natural superiority of one man over another.
But that we may be satisfied, that to this kind of reasoning, in
its earliest or simplest form, little or no reflection is necessary,
let it be observed, that it is now universally admitted by opticians,
that it is not purely from sight, but from sight aided byexperience,
that we derive our notions of the distance of visible objects from
the eye. The sensation, say they, is instantaneously followed by a
conclusion or judgment founded on experience. The point is determined
from the different phases of the object found, in former trials, to
be connected with different distances, or from the effort that
accompanies the different conformations we are obliged to give the
organs of sight, in order to obtain a distinct vision of the object.
Now, if this be the case, as I think hath been sufficiently evinced
of late, it is manifest that this judgment is so truly instantaneous,
and so perfectly the result of feeling and association, that the
forming of it totally escapes our notice. Perhaps in no period of
life will you find a person, that, on the first mention of it, can be
easily persuaded that he derives this knowledge from experience.
Every man will be ready to tell you that he needs no other witnesses
than his eyes, to satisfy him that objects are not in contact with
his body, but are at different distances from him as well as from one
another. So passive is the mind in this matter, and so rapid are the
transitions which, by this ideal attraction, she is impelled to make,
that she is, in a manner, unconscious of her own operations. There is
some ground to think, from the exact analogy which their organs bear
to ours, that the discovery of distance from the eye is attained by
brutes in the same manner as by us. As to this, however, I will not
be positive. But though, in this way, the mind acquires an early
perception of the most obvious and necessary truths, without which
the bodily organs would be of little use; in matters less important
her procedure is much slower, and more the result of voluntary
application; and as the exertion is more deliberate, she is more
conscious of her own activity, or, at least, remembers it longer. It
is then only that in common style we honour her operation with the
name of reasoning; though there is no essential difference between
the two cases. It is true, indeed, that the conclusions in the first
way, by which also in infancy we learn language, are commonly more to
be regarded as infallible, than those effected in the second.
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