When Materialists affirm, as they do, the existence of one only substantive being in Nature, and represent all our mental phenomena as the mere results of physical organization, they assume that "matter," at least, is a real entity; that it is a substance or substratum in which certain powers or qualities inhere; and that its existence, as such, is evident and undeniable. We are entirely relieved, therefore, by their own admission or assumption, from the necessity of discussing the more general problem of Ontology; the problem, whether we can prove the existence of any being, properly so called, from a mere series of phenomena, a succession of appearances. They virtually admit, since they evidently assume, that the phenomena must have a substance under them, the qualities a substratum in which they inhere. Now, the very same reason which warrants, or rather obliges them to recognize "matter" as a substance and not as a shadow,—as an entity which really exists and manifests itself by its properties and effects,—must equally warrant, or rather oblige them to recognize "mind" or "spirit" also as a distinct substantive being, unless it can be shown either that its properties are the same with those of matter, or that they may be accounted for by some peculiar modification of matter, some law of physical organization. There can be no reason for admitting the existence of "matter" as a substance, which does not apply also to the existence of "mind" as a distinct substance, if it shall be found that their properties are essentially different. We know, and can know, nothing of substance otherwise than by its properties or powers: we know nothing of "matter,"—it would, in fact, be to us non-existent, but for its extension, solidity, and other properties; we know nothing of "mind,"—it would equally be to us non-existent, but for its consciousness, its thoughts, feelings, and desires; and if it be right to ascribe the one set of properties to a substantive being, called "matter," it cannot be wrong to ascribe the other set of properties also to a substantive being, called "mind."
If it could be shown, indeed, that the properties of the one substance might either be identified with, or accounted for, by those of the other; if animal feeling could be identified with or derived from, mere physical impulse; if intellectual thought could be reduced to material motion; if desire and aversion, hope and fear could be explained by the natural laws of attraction and repulsion, then we might blend the two substances into one, and speak of "mind" as a mere modification of "matter." But as long as the properties or powers by which alone any substance can be known are seen to be generically different, we cannot confound the substances themselves, or reduce them to one category, without violating the plainest rules of philosophical inquiry.
And yet to these rules Dr. Priestley refers, as if they warranted the conclusions at which he had arrived. He desires his readers "to recur to the universally received rules of philosophizing, such as are laid down by Sir Isaac Newton at the beginning of his third book of "Principia." The first of these rules, as laid down by him, is that we are to admit no more causes than are sufficient to explain appearances; and the second is, that to the same effect we must, as far as possible, assign the same cause." We cheerfully accept these canons of philosophical inquiry; and it is just because no one substance is sufficient, in our estimation, to account for all the appearances, that we equally reject the "spiritualism" of Berkeley, who would resolve all phenomena into "mind," and the "materialism" of Priestley, who would resolve all phenomena into "matter." Matter and Mind may, indeed, be said to resemble each other in some respects,—in their being equally existent, equally created, and equally dependent; but their essential properties are generically different, for there is no identity, but a manifest and undeniable diversity, between thought, feeling, desire, volition, and conscience, and the various qualities or powers belonging to matter, such as extension, solidity, and vis inertiæ, or even the powers of attraction and repulsion. On the ground of this manifest difference between the properties by which alone any substance makes itself known, we hold ourselves warranted to affirm that the "mind" is immaterial, and to ascribe mental phenomena to a distinct substantive being, not less than the material phenomena of Nature.
Some ingenious thinkers, on both sides of the question, have not been fully satisfied with this method of stating the grounds of our opinion. It has been said by our opponents, that if we found merely on the acknowledged difference between two sets of properties or phenomena, while we admit that the substance or substratum is in itself entirely unknown to us, or known only through the medium of the properties to which we refer,—then the dispute becomes a purely verbal one, and can amount to nothing more than this, whether a substance of whose essence we are entirely ignorant should be called by the name of "matter" or by the name of "spirit." But the dispute is not a purely verbal one, even on the suppositions which have been stated. For it is essential to a right "philosophy of nature," that every substance possessing peculiar properties should have a distinctive name. Thus, even in the material world itself, we distinguish sulphur from soda, gold from granite, and magnesia from electricity or odyle. Why? Because, while they have some properties in common, in virtue of which we rank them in the same category as "material substances," they have, severally, certain distinctive or peculiar characteristics, which forbid us to call the one by the same name as the other. And for precisely the same reason, when we find another class of properties and powers existing in certain beings, which are totally different from those belonging to mere material substances,—incapable not only of being identified with them, but also of being accounted for by means of them,—we are equally warranted in ascribing these properties to a substance, and in affirming that this substance, of which we know nothing except through its properties, is radically different from "matter." That there is something more than a mere verbal difference between us and our opponents might seem to be admitted by themselves, when they evince so much zeal in assailing our position and defending their own; but it becomes strikingly apparent as soon as we extend our inquiry so as to embrace the grand question respecting the distinction, if any, between God and the material universe.
Some, again, who are substantially, at least in all important respects, on our side of the question, have not been satisfied with showing that the two sets of properties are generically different, and that the same reason exists for ascribing the one to a distinct substantive being called "mind," as for ascribing the other to a substantive being called "matter." They have been anxious to advance a step further; and to show that the two sets of properties are mutually exclusive, and that they could not possibly coexist in the same subject. This is the declared object of Baxter's Work on the Soul, which professes to prove that the only power belonging to "matter," namely, its vis inertiæ, or resistance to any change in its present state, is inconsistent with its possession of any active power. It is not held sufficient to show that the properties are generically different, and that the substances in which these properties inhere may and should be designated by distinct names, as matter and spirit, soul and body; but it must be further proved that they are so heterogeneous and inconsistent as to be mutually exclusive, and incapable of coexisting in the same substance. To a certain extent, we think this mode of reasoning may be admitted. We do not conceive that "vis inertiæ" is the only property belonging to matter, or that it is necessarily exclusive of attraction and repulsion, and the other powers which may belong to its specific varieties; but we do conceive that the "vis inertiæ" of mere matter is utterly inconsistent with the self-activity, the self-moving power, which belongs to "mind:" and we are confirmed in this conviction by the anxiety which our opponents have evinced to explain the phenomena of mind by purely mechanical laws, and to establish a system, not of moral, but of material necessity, in opposition to the doctrine of man's spontaneity and freedom. We are further of opinion, that extension cannot be predicated of "mind," without also being predicated of "thought;" and that to ascribe it to either would lead to ridiculous absurdities, such as have been noted, and perhaps caricatured, by Dr. Thomas Brown. We think, too, that the unity and continuity of consciousness, with the intimate sense of personal identity, that belongs to all rational and responsible beings, are utterly irreconcilable with the continual flux and mutation that are incident to matter, and that they cannot be accounted for without the supposition of a distinct substance, existing the same throughout all the changes that occur in the material receptacle in which it dwells. To this extent we think that the argument is alike legitimate and valid; but when it goes beyond this, and attempts either to divest matter of all active properties, or to demonstrate that, in the very nature of things, sensation and thought could not possibly be annexed to a material substance, we think that it advances beyond the real exigencies of the case, and that it undertakes a task which is somewhat too arduous for our present powers,—a task which many of the ablest advocates of Immaterialism would humbly, but firmly, decline.
In this connection, it may be useful to remark that it is only with reference to this advanced and more arduous part of the general argument, that such writers as Locke and Bonnet, whose authority is often pleaded in opposition to our views, ever felt the slightest difficulty. They were both "Immaterialists," because they both discerned the radical difference between mental and material phenomena, and because they both admitted the reasonableness of ascribing them, respectively, to a distinct substance. But they were not convinced by the more metaphysical arguments of those who professed to show that none of the phenomena of "mind" could possibly be exhibited by matter, or, at least, they declined to take that ground. That Locke was an Immaterialist is evident from many passages in his writings. "By putting together," he says, "the ideas of thinking, perceiving, liberty and power of moving themselves and other things, we have as clear a perception and notion of immaterial substances as we have of material. For putting together the ideas of thinking and willing, &c., joined to substance, of which we have no distinct idea, we have the idea of an immaterial spirit; and by putting together the ideas of coherent solid parts and a power of being moved, joined with substance, of which likewise we have no positive idea, we have the idea of matter: the one is as clear and distinct an idea as the other."[165] But notwithstanding this explicit statement, he demurred to the doctrine of those who maintained that the power of thinking could not possibly be superadded to matter, and this because he deemed it presumptuous to set limits to the Divine omnipotence, or to pronounce any judgment on a question of that kind. "We have the ideas of matter and thinking, but possibly shall never be able to know whether any mere material being thinks or no; it being impossible for us, by the contemplation of our own ideas, without Revelation, to discover whether Omnipotency has not given to some systems of matter, fitly disposed, a power to perceive and think.... I see no contradiction in it that the first eternal thinking Being should, if He pleased, give to certain systems of created senseless matter, put together as He sees fit, some degrees of sense, perception, and thought."[166]
In these and similar passages, Locke did not mean, we think, to retract or modify the doctrine which he had taught respecting the radical distinction betwixt mind and matter; he intended merely to intimate that, in adopting that doctrine, he proceeded on grounds different from those which had been assumed by some other writers; that his belief rested mainly on the essential difference between the properties belonging to the two substances, and not on the mere metaphysical arguments by which some had attempted to prove that God himself could not impart to matter the power of thinking. He shrunk from pronouncing a positive decision on this one point; and yet his words have ever since been quoted with triumph by the advocates of Materialism as affording a virtual sanction to the possibility at least of that for which they contend. And on the same account, Locke has been severely blamed by some modern "spiritualists." Mr. Carlyle, speaking of "Hartley's and Darwin's, and all the possible forms of Materialism,—the grand Idolatry, as we may rightly call it, by which at all times the true worship, that of the invisible, has been polluted and withstood"—adds the following characteristic remarks: "Locke, himself a clear, humble-minded, patient, reverent, nay religious man, had paved the way for banishing religion from the world. Mind, by being modelled in men's imaginations into a Shape, a Visibility, and reasoned of as if it had been some composite, divisible, and reunitable substance, some finer chemical salt, or curious piece of logical joinery, began to lose its immaterial, mysterious, divine, though invisible character: it was tacitly figured as something that might, were our organs fine enough, be seen. Yet who had ever seen it? who could ever see it? Thus, by degrees, it passed into a Doubt, a Relation, some faint Possibility, and, at last, into a highly probably Nonentity. Following Locke's footsteps, the French had discovered that 'as the stomach secretes chyle, so does the brain secrete thought.'"[167]
The sentiments of Bonnet of Geneva, as stated in his "Palingenesie," are substantially in accordance with those of Locke, and have met with similar treatment. He is not a Materialist; he admits a real distinction, as well as a close union, between the soul and the body; he speaks even of the possible existence of disembodied souls or pure spirits; he affirms the immateriality of the thinking principle; and expressly assigns his reasons for not being a Materialist.[168] But he appears to have thought, as Locke did, that possibly the power of thinking might be superadded to matter, by the Creator's omnipotent will, and that there is nothing in this supposition which could seriously affect either the doctrine of Theism or the "immortality" of man. And hence he affirmed, in words which Dr. Priestley selected for the motto of his "Disquisitions," that "if any one should ever demonstrate the soul to be material, far from being alarmed at this, we should only admire the power which could give to matter the power of thinking."
We conceive that the language both of Locke and Bonnet on this particular point amounts to a dangerous and very unnecessary concession. Were it meant merely to affirm that God could so unite a thinking spiritual being with a material organism, as to make the two mutually dependent and subservient, this is no more than is admitted by all the advocates of Immaterialism, and it is actually exhibited in the constitution of human nature. But if it were meant to admit that the power of "thinking" and "willing" might be superadded as a property or quality to matter itself, without any substantive being other than matter as a substratum, then we conceive it to be at variance with the grounds on which Locke and Bonnet themselves had previously declared their belief in the distinct existence both of matter and spirit. We shall only add, that the prejudice against our doctrine, which is founded on the union of two substances apparently so heterogeneous as mind and matter in the same person, is, to say the least, fully counterbalanced by the difficulty, incident to the theory, of demonstrating the coexistence of two sets of properties, apparently so diverse and disparate as thought and extension, "vis inertiæ" and spontaneity, in the same substance.
On the whole, we conclude that the same reason which warrants us in ascribing certain properties or phenomena to a distinct substance called "matter," equally warrants us in ascribing certain other properties or phenomena to a distinct substance called "mind;" and that the difference between their properties and phenomena is so great as to justify the belief that the substances are different, and ought to be denominated by distinctive names.