SECTION II.

Of certain natural Prejudices, which feem to have given rife to the common Theories of Perception.

IT.

T feems now to be pretty generally agreed among philofophers, that there is no inftance in which we are able to perceive a neceffary connexion between two fucceffive events; or to comprehend in what manner the one proceeds from the other, as its caufe. From experience, indeed, we learn, that there are many events, which are conftantly conjoined, fo that the one invariably follows the other: but it is poffible, for any thing we know to the contrary, that this connexion, though a conftant one, as far as our obfervation has reached, may not be a neceffary connexion; nay, it is poffible, that there may be no neceffary connexions among any of the phenomena we fee and, if there are any fuch connexions exifting, we may reft affured that we shall never be able to difcover them *..

I fhall endeavour to fhew, in another part of this work, that the doctrine I have now ftated does not lead to these sceptical conclufions, concerning the existence of a First Cause, which an author of great ingenuity has attempted to deduce from it--At prefent, it is fufficient for my purpose to remark, that the word caufe is used, both by philofophers and the

vulgar, in two fenfes, which are widely different.When it is faid, that every change in nature indicates the operation of a caufe, the word cause expreffes fomething which is fuppofed to be neceffarily connected with the change; and without which it could not have happened. This may be called the metaphyfical meaning of the word; and fuch causes may be called metaphyfical or efficient causes.-In natural philosophy, however, when we speak of one thing being the cause of another, all that we mean is, that the two are conftantly conjoined; so that, when we fee the one, we may expect the other. These conjunctions we learn from experience alone; and without an acquaintance with them, we could not accommodate our conduct to the established course of nature. The causes which are the objects of our investigation in natural philosophy, may, for the fake of diftinction, be called phyfical caufes.

I am very ready to acknowledge, that this doctrine, concerning the object of natural philofophy, is not altogether agreeable to popular prejudices. When a man, unaccustomed to metaphyfical fpeculations, is told, for the first time, that the fcience of phyfics gives us no information concerning the efficient caufes of the phenomena about which it is employed, he feels fome degree of furprise and mortification. The natural bias of the mind is furely to conceive phyfical events as somehow linked together; and material fubftances, as poffeffed of certain powers and virtues, which fit them to produce particular effects. That we have no reafon to believe this to be the cafe, has been fhewn in a very particular manner by Mr.

Hume,

Hume, and by other writers; and muft, indeed, appear evident to every person, on a moment's reflection. It is a curious queftion, what gives rife to the prejudice?

In stating the argument for the existence of the Deity, feveral modern philofophers have been at pains to illustrate that law of our nature, which leads us to refer every change we perceive in the universe, to the operation of an efficient caufe *.-This reference is not the refult of reafoning, but neceffarily accompanies the perception, fo as to render it impoffible for us to fee the change, without feeling a conviction of the operation of fome caufe by which it was produced; much in the fame manner in which we find it to be impoffible to conceive a fenfation, without being impreffed with a belief of the existence of a fentient being. Hence, I apprehend, it is, that when we see two events conftantly conjoined, we are led to affociate the idea of caufation, or efficiency, with the former, and to refer to it that power or energy by which the change was produced; in confequence of which affociation, we come to confider philofophy as the knowledge of efficient caufes; and lofe fight of the operation of mind, in producing the A phenomena of nature. It is by an affociation fome. what fimilar, that we connect our fenfations of colour, with the primary qualities of body. A moment's reflection must fatisfy any one, that the fenfation of colour can only refide in a mind; and yet our natural bias is furely to connect colour with extenfion and

See, in particular, Dr. Reid's Effays on the Intellectual Powers of Man.

figure, and to conceive white, blue, and yellow, as fomething spread over the furfaces of bodies. In the fame way, we are led to affociate with inanimate matter, the ideas of power, force, energy, and caufation; which are all attributes of mind, and can exift in a mind only.

The bias of our nature is strengthened by another affociation. Our language, with respect to cause and effect, is borrowed by analogy from material objects. Some of these we see scattered about us, without any connexion between them; fo that one of them may be removed from its place, without disturbing the rest. We can, however, by means of fome material vincu lum, connect two or more objects together; fo that whenever the one is moved, the others fhall follow. In like manner, we fee fome events, which occafionally follow one another, and which are occafionally dif joined we fee others, where the fucceffion is conftant and invariable. The former we conceive to be analogous to objects which are loofe, and unconnected with each other, and whofe contiguity in place, is ow. ing merely to accidental pofition; the others to objects which are tied together by a material vinculum. Hence we transfer to fuch events, the fame language which we apply to connected objects. We speak of a connexion between two events, and of a chain of causes and effects *.

That this language is merely analogical, and that we know nothing of phyfical events, but the laws which regulate their fucceflion, muft, I think, appear

See Note [D].

very obvious to every person who takes the trouble to reflect on the subject; and yet it is certain, that it has mifled the greater part of philofophers; and has had a furprising influence on the fyftems, which they have formed in very different departments of science.

A few remarks, on fome of the mistaken conclufions, to which the vulgar notions concerning the connexions among phyfical events have given rise, in natural philofophy, will illuftrate clearly the origin of the common theories of perception; and will, at the fame time, fatisfy the reader, with respect to the train of thought which fuggefted the foregoing ob. servations.

The maxim, that nothing can act but where it is, and when it is, has always been admitted, with respect to metaphyfical or efficient causes. "What"ever objects," fays Mr. Hume, "are confidered as "causes or effects, are contiguous; and nothing can operate in a time or place, which is ever fo little " removed from thofe of its existence." We may "therefore (he adds) confider the relation of conti"guity as effential to that of caufation."-But although this maxim fhould be admitted, with refpect to causes which are efficient, and which, as fuch, are neceffarily connected with their effects, there is furely no good reason for extending it to phyfical caufes, of which we know nothing, but that they are the constant forerunners and figns of certain natural events. It may, indeed, be improper, according to this doctrine, to retain the expreffions, cause and effect, in natural philosophy; but, as long as the present language upon the subject continues in ufe, the propriety of its