Sect. VFirst, I observe, that the word, action, according to this explication of it, can never justly be applied to any perception, as derived from a mind or thinking substance. Our perceptions are all really different, and separable, and distinguishable from each other, and from everything else, which we can imagine: and therefore it is impossible to conceive, how they can be the action or abstract mode of any substance. The instance of motion, which is commonly made use of to shew after what manner perception depends, as an action, upon its substance, rather confounds than instructs us. Motion to all appearance induces no real nor essential change on the body, but only varies its relation to other objects. But betwixt a person in the morning walking a garden with company, agreeable to him; and a person in the afternoon inclosed in a dungeon, and full of terror, despair, and resentment, there seems to be a radical difference, and of quite another kind, than what is produced on a body by the change of its situation. As we conclude from the distinction and separability of their ideas, that external objects have a separate existence from each other; so when we make these ideas themselves our objects, we must draw the same conclusion concerning them, according to the precedent reasoning. At least it must be confest, that having idea of the substance of the soul, it is impossible for us to tell how it can admit of such differences, and even contrarieties of perception without any fundamental change; and consequently can never tell in what sense perceptions are actions of that substance. The use, therefore, of the word, action, unaccompanyed with any meaning, instead of that of modification, makes no addition to our knowledge, nor is of any advantage to the doctrine of the immateriality of the soul.

I add in the second place, that if it brings any advantage to that cause, it must bring an equal to the cause of atheism. For do our Theologians pretend to make a monopoly of the word, action, and may not the atheists likewise take possession of it, and affirm that plants, animals, men, &c. are nothing but particular actions of one simple universal substance, which exerts itself from a blind and absolute necessity? This you'll say is utterly absurd. I own it is unintelligible; but at the same time assert, according to the principles above-explained, that it is impossible to discover any absurdity in the supposition, that all the various objects in nature are actions of one simple substance, which absurdity will not be applicable to a like supposition concerning impressions and ideas.

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, it is commonly said in the schools, however varyed, 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, it is 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. It is 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 any idea of thought or perception, it is 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 it is 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;[13] I have inferred from these principles, 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 center, 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, it is 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 apparent connexion in the one case than in the other. But as this latter conclusion is contrary to evident experience, and as it is 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 it is impossible motion can ever produce thought, or a different position of parts give rise to a different passion or reflection. Nay it is not only possible we may have such an experience, but it is 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.

[13] Part III. Sect. 15.

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 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[14] several philosophers with relation to all the actions of the mind, except volition, or rather an inconsiderable part of volition; though it is 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.