Page 89 of 96

From these hypotheses concerning the substance and local conjunction of our perceptions, we may pass to another, which is more intelligible than the former, and more important than the latter, viz. concerning the cause of our perceptions. Matter and motion, 'tis commonly said in the schools, however varied, are still matter and motion, and produce only a difference in the position and situation of objects. Divide a body as often as you please, 'tis still body. Place it in any figure, nothing ever results but figure, or the relation of parts. Move it in any manner, you still find motion or a change of relation. 'Tis absurd to imagine, that motion in a circle, for instance, should be nothing but merely motion in a circle; while motion in another direction, as in an ellipse, should also be a passion or moral reflection: that the shocking of two globular particles should become a sensation of pain, and that the meeting of two triangular ones should afford a pleasure. Now as these different shocks and variations and mixtures are the only changes of which matter is susceptible, and as these never afford us[Pg 315] any idea of thought or perception, 'tis concluded to be impossible, that thought can ever be caused by matter.

Few have been able to withstand the seeming evidence of this argument; and yet nothing in the world is more easy than to refute it. We need only reflect on what has been proved at large, that we are never sensible of any connexion betwixt causes and effects, and that 'tis only by our experience of their constant conjunction, we can arrive at any knowledge of this relation. Now, as all objects, which are not contrary, are susceptible of a constant conjunction, and as no real objects are contrary; I have inferred from these principles,[14] that to consider the matter a priori, any thing may produce any thing, and that we shall never discover a reason, why any object may or may not be the cause of any other, however great, or however little the resemblance may be betwixt them. This evidently destroys the precedent reasoning concerning the cause of thought or perception. For though there appear no manner of connexion betwixt motion or thought, the case is the same with all other causes and effects. Place one body of a pound weight on one end of a lever, and another body of the same weight on another end; you will never find in these bodies any principle of motion dependent on their distances from the centre, more than of thought and perception. If you pretend, therefore, to prove, a priori, that such a position of bodies can never cause thought; because, turn it which way you will, 'tis nothing but a position of bodies; you must, by the same course of reasoning conclude, that it can never produce motion; since there is no more[Pg 316] apparent connexion in the one case than in the other. But as this latter conclusion is contrary to evident experience, and as 'tis possible we may have a like experience in the operations of the mind, and may perceive a constant conjunction of thought and motion; you reason too hastily, when, from the mere consideration of the ideas, you conclude that 'tis impossible motion can ever produce thought, or a different position of parts give rise to a different passion or reflection. Nay, 'tis not only possible we may have such an experience, but 'tis certain we have it; since every one may perceive, that the different dispositions of his body change his thoughts and sentiments. And should it be said, that this depends on the union of soul and body, I would answer, that we must separate the question concerning the substance of the mind from that concerning the cause of its thought; and that, confining ourselves to the latter question, we find, by the comparing their ideas, that thought and motion are different from each other, and by experience, that they are constantly united; which being all the circumstances that enter into the idea of cause and effect, when applied to the operations of matter, we may certainly conclude, that motion may be, and actually is, the cause of thought and perception.

There seems only this dilemma left us in the present case; either to assert, that nothing can be the cause of another, but where the mind can perceive the connexion in its idea of the objects: or to maintain, that all objects which we find constantly conjoined, are upon that account to be regarded as causes and effects. If we choose the first part of the dilemma, these are the consequences. First, we in reality affirm, that there is no such thing in the universe as a cause or productive[Pg 317] principle, not even the Deity himself; since our idea of that Supreme Being is derived from particular impressions, none of which contain any efficacy, nor seem to have any connexion with any other existence. As to what may be said, that the connexion betwixt the idea of an infinitely powerful Being and that of any effect, which he wills, is necessary and unavoidable; I answer, that we have no idea of a Being endowed with any power, much less of one endowed with infinite power. But if we will change expressions, we can only define power by connexion; and then in saying, that the idea of an infinitely powerful Being is connected with that of every effect which he wills, we really do no more than assert, that a Being, whose volition is connected with every effect, is connected with every effect; which is an identical proposition, and gives us no insight into the nature of this power or connexion. But, secondly, supposing that the Deity were the great and efficacious principle which supplies the deficiency of all causes, this leads us into the grossest impieties and absurdities. For upon the same account that we have recourse to him in natural operations, and assert that matter cannot of itself communicate motion, or produce thought, viz. because there is no apparent connexion betwixt these objects; I say, upon the very same account, we must acknowledge that the Deity is the author of all our volitions and perceptions; since they have no more apparent connexion either with one another, or with the supposed but unknown substance of the soul. This agency of the Supreme Being we know to have been asserted by several philosophers[15] with relation to all[Pg 318] the actions of the mind, except volition, or rather an inconsiderable part of volition; though 'tis easy to perceive, that this exception is a mere pretext, to avoid the dangerous consequences of that doctrine. If nothing be active but what has an apparent power, thought is in no case any more active than matter; and if this inactivity must make us have recourse to a Deity, the Supreme Being is the real cause of all our actions, bad as well as good, vicious as well as virtuous.

Thus we are necessarily reduced to the other side of the dilemma, viz. that all objects, which are found to be constantly conjoined, are upon that account only to be regarded as causes and effects. Now, as all objects which are not contrary, are susceptible of a constant conjunction, and as no real objects are contrary; it follows, that, for ought we can determine by the mere ideas, any thing may be the cause or effect of any thing; which evidently gives the advantage to the materialists above their antagonists.

To pronounce, then, the final decision upon the whole: the question concerning the substance of the soul is absolutely unintelligible: all our perceptions are not susceptible of a local union, either with what is extended or unextended; there being some of them of the one kind, and some of the other: and as the constant conjunction of objects constitutes the very essence of cause and effect, matter and motion may often be regarded as the causes of thought, as far as we have any notion of that relation.