Cartesianism was sufficiently obnoxious to the divines to provoke their wrath; and yet, from some of its peculiarities, it has found many opponents amongst the philosophical party. The Cartesian philosophy is founded on two great principles, the one metaphysical, the other physical. The metaphysical is Des Cartes's foundation-stone—the "I think, therefore I am." This has been warmly attacked as not being logical. Des Cartes said his existence was a fact—a fact above and beyond all logic; logic could neither prove nor disprove it. The Cogito ergo Sum was not new itself, but it was the first stone of a new building—the first step in a new road: from this fact Des Cartes tried to reach another, and from that others.
The physical principle is that nothing exists but substance, which he makes of two kinds—the one a substance that thinks, the other a substance extended. Actual thought and actual extension are the essence of substance, so that the thinking substance cannot be without some actual thought, nor can anything be retrenched from the extension of a thing, without taking away so much of its actual substance.
In his physical speculations, Des Cartes has allowed his imagination to run very wild. His famous theory of vortices is an example of this. Assuming extension to be the essence of substance, he denied the possibility of a vacuum by that assumption; for if extension be the essence of substance, wherever extension is, there substance must be. This substance he assumes to have originally been divided into equal angular particles, each endowed with an equal degree of motion; several systems or collections of these particles he holds to have a motion about certain equidistant points, or centres, and that the particles moving round these composed so many vortices. These angular particles, by their intestine motions, he supposes to become, as it were, ground into a spherical form; the parts rubbed off are called matter of the first element, while the spherical globules he calls matter of the second element; and since there would be a large quantity of this element, he supposes it to be driven towards the centre of each vortex by the circular motion of the globules, and that there it forms a large spherical body such as the suu. This sun being thus formed, and moving about its own axis with the common matter of the vortex, would necessarily throw out some parts of its matter, through the vacuities of the globules of the second element constituting the vortex; and this especially at such places as are farthest from its poles: receiving, at the same time in, by these poles, as much as it loses in its equatorial parts. And, by these means, it would be able to carry round with it those globules that are nearest, with the greater velocity; and the remoter, with less. And, further: those globules which are nearest the centre of the sun, must be smallest; because, were they greater, or equal, they would, by reason of their velocity, have a greater centrifugal force, and recede from the centre. If it should happen that any of these sun-like bodies, in the centres of the several vortices, should be so in-crusted and weakened, as to be carried about in the vortex of the true sun: if it were of less solidity, or had less motion than the globules towards the extremity of the solar vortex, it would descend towards the sun, till it met with globules of the same solidity, and susceptible of the same degree of motion with itself* and thus, being fixed there, it would be for ever after carried about by the motion of the vortex, without either approaching any nearer to, or receding from the sun, and so become a planet. Supposing, then, all this, we are next to imagine that our system was at first divided into several vortices, in the centre of each of which was a lucid spherical body; and that some of these being gradually incrustated, were swallowed up by others which were larger, and more powerful, till at last they were all destroyed and swallowed up by the biggest solar vortex, except some few which were thrown off in right lines from one vortex to another, and so became comets. It should also be added, that in addition to the two elements mentioned above, those particles which may yet exist, and be only in the course of reduction to their globular form an it still retain their angular proportions, form a third element.
This theory has found many opponents; but in this state of our work we conceive our duty to be that of giving a simple narrative of the philosopher's ideas, rather than a history of the various criticisms upon those ideas, the more especially as our pages scarcely afford room for such a mode of treatment.
Having formed his method, Des Cartes proceeded to apply it. The basis of certitude being consciousness, he interrogated his consciousness, and found that he had an idea of a substance infinite, eternal, immutable, independent, omniscient, omnipotent. This he called an idea of God: he said, "I exist as a miserably imperfect finite being, subject to change—ignorant, incapable of creating anything—I find by my finitude that I am not the infinite; by my liability to change that I am not the immutable; by my ignorance that I am not the omniscient: in short, by my imperfection, that I am not the perfect. Yet an infinite, immutable, omniscient, and perfect being must exist, because infinity, immutability, omniscience, and perfection are applied as correlatives in my ideas of finitude, change, etc. God therefore exists: his existence is clearly proclaimed in my consciousness, and therefore ceases to be a matter of doubt any more than the fact of my own existence. The conception of an infinite being proved his real existence, for if there is not really such a being I must have made the conception; but if I could make it I can also unmake it, which evidently is not true; therefore there must be externally to myself, an archetype from which the conception was derived.".... "All that we clearly and distinctly conceive as contained in anything is true of that thing."
"Now, we conceive clearly and distinctly that the existence of God is contained in the idea we have of him: ergo—God exists."—(Lewes's Bio. Hist. Phil.)
Des Cartes was of opinion that his demonstrations of the existence of God "equal or even surpass in certitude the demonstrations of geometry." In this opinion we must confess we cannot share. He has already told us that the basis of all certitude is consciousness—that whatever is clearly and distinctly conceived, must be true—that imperfect and complex conceptions are false ones. The first proposition, all must admit, is applicable to themselves. I conceive a fact clearly and distinctly, and, despite all resistance, am compelled to accept that fact; and if that fact be accepted beyond doubt, no higher degree of certainty can be attained, That two and two are four—that I exist—are facts which I never doubt. The Cogito ergo Sum is irresistible, because indubitable; but Cogito ergo Deus est is a sentence requiring much consideration, and upon the face of it is no syllogism, but, on the contrary, is illogical. If Des Cartes meant "I" am conscious that I am not the whole of existence, he would be indisputable; but if he meant that "I" can be conscious of an existence entirely distinct, apart from, and external to, that very consciousness, then his whole reasoning from that point appears fallacious.
We use the word "I" as given by Des Cartes. Mill, in his "System of Logic," says, "The ambiguity in this case is in the pronoun I, by which in one place is to be understood my will: in another the laws of my nature. If the conception, existing as it does in my mind, had no original without, the conclusion would unquestionably follow that '1' had made it—that is, that the laws of my nature had spontaneously evolved it; but that my will made it would not follow. Now, when Des Cartes afterwards adds that I cannot unmake the conception, he means that I cannot get rid of it by an act of my will, which is true; but is not the proposition required. That what some of the laws of my nature have produced, other laws, or those same laws in other circumstances, might not subsequently efface, he would have found it difficult to establish."
Treating the existence of God as demonstrated from the a priori idea of perfection and infinity, and by the clearness of his idea of God's existence, Des Cartes then proceeds to deal with the distinction between body and soul. To prove this distinction was to him an easy matter. The fundamental and essential attribute of substance must be extension, because we can denude substance of every quality but that of extension; this we cannot touch without at the same time affecting the substance.. The fundamental attribute of mind is thought; it is in the act of thinking that the consciousness of existence is revealed; to be without thought would be to be without consciousness.
Des Cartes has given us, among others, the axiom "That two substances are really distinct when their ideas are complete, and no way imply each other. The idea of extension is complete and distinct from the idea of thought, which latter is also clear and distinct by itself. It follows, therefore, that substance and mind are distinct in essence."