"A classification of systems of philosophy according to the cosmological conceptions governing them has actually been made. It is founded on a consideration of the differences among philosophers as to what that totality of existence is which is to be accepted as really vouched for by Mind. All agree, as we have said, that Mind is the sole voucher for anything; but philosophers are divisible into schools according to the various views they have taken of the constitution of that phenomenal Universe, that Cosmos, that total round of things, of which we have a recurring assurance in every act of perception, and which is orbed forth more or less fully for each man in his wider contemplations.
"The popular or habitual conception of mankind in general is that there are two distinct worlds mixed up in the phenomenal Cosmos—a world of Mind, consisting of multitudes of individual minds, and a world of Matter, consisting of all the extended immensity and variety of material objects. Neither of these worlds is thought of as begotten of the other, but each of them as existing independently in its own proper nature and within its own definite bounds, though they traffic with each other at present. Sweep away all existing minds, and the deserted Earth would continue to spin round all the same, still whirling its rocks, trees, clouds, and all the rest of its material pomp and garniture, alternately in the sunshine and in the depths of the starry stillness. Though no eye should behold, and no ear should hear, there would be evenings of silver moonlight on the ocean-marge, and the waves would roar as they broke and retired. On the other hand, suppose the entire fabric of the material Universe abolished and dissolved, and the dishoused population of spirits would still somehow survive in the imaginable vacancy. If this second notion is not so easy or common as the first, it still virtually belongs to the popular conception of the contents or constitution of the Cosmos. The conception is that of a Natural Dualism, or of the contact in every act of perception of two distinct spheres, one an internal perceiving mind, and the other an external world composed of the actual and identical objects which this mind perceives.
"On the first exercise of philosophic thought, however, this conception is blurred. An immense quantity of what we all instinctively think of as really existing out of ourselves turns out, on investigation, not to exist at all as we fancy it existing, but to consist only of affections of the perceiving mind. The redness of the rose is not a real external thing, immutably the same in itself; it is only a certain peculiar action on my physiology which the presence of an external cause or object seems to determine. Were my physiology different, the action would be different, though the cause or object remained the same. Indeed, there are persons in whom the presence of a rose occasions no sensation of redness such as is known to me, but a much vaguer sensation, not distinguishable from what I should at once distinguish as greenness. And, as colour is thus at once detected as no external independently-existing reality, but only a recurring physiological affection of myself and other sentient beings like myself, so with a thousand other things which, by habit or instinct, I suppose as externally and independently existing. When I imagine the depopulated Earth still wheeling its inanimate rotundity through the daily sunshine and the nocturnal shadow, or one of its bays still resonant in moonlit evenings with the roar of the breaking waves, it is because, in spite of myself, I intrude into the fancy the supposition of a listening ear, and a beholding eye analogous to my own. It is only by a strong effort that I can realize that a great deal at least of what I thus think of as the goings-on of things by themselves is not and cannot be their goings-on by themselves, but consists at the utmost of effects interbred between them and a particular sentiency in the midst of them. But the effort may be made; and, when it is made repeatedly, in a great many directions, and with reference to a great many of the so-called properties of matter, the inevitable result for the philosophic mind is that the popularly-imagined substance of a real external world finds itself eaten away or corroded, at least to a certain depth. So far philosophers are agreed. It is when they proceed to consider to what depth the popularly-imagined substance of the real external world is thus eaten away, or accounted for, that they begin to differ.
"Some philosophers, departing as little as may be from the popular judgment, suppose that, however much of the apparent external world may be resolved into affections of the subjective sentiency, there still remains an objective residue of such primary qualities as extension, figure, divisibility, mobility, etc., belonging to external matter itself, and by the direct and immediate cognizance of which the mind is brought face to face with external substance, and knows something of its real goings-on. Philosophers of this school are known generally as Realists. More numerous, however, are those who, not allowing an objective and independent reality even to the so-called primary qualities of matter, but believing them as well as colour, odour, or savour, to be only affections of the sentiency, deny that the mind is in any sense brought face to face with real external things such as they seem in the act of perception. To thinkers of this school there has been given the general name of Idealists. This broad distinction of Philosophers cosmologically into Realists and Idealists is so far convenient enough. Cosmologically, or in respect of this present Universe of ours, with its dualism of Mind and Matter, every man must declare himself either a Realist or an Idealist, if he understands the meanings attached to these terms. The distinction has reference solely to his notion of the so-called external or material world in its relations to the perceiving mind. If he abides, though only in part, by the popular conception, and regards the material world as a substantial reality independent of the perceiving mind, and which the mind, according to its powers, presses against and directly apprehends in every act of perception, then he is a Realist. If, on the other hand, he cannot see that there need be asserted any external material world with such characters as we attribute to it, but supposes that our unanimous agreement in the imagination of such an external world is merely a habit of our own sentiency, projecting its own ideas or affections outwards, and giving them a body, then he is an Idealist." Masson, "Recent British Philosophy," pp. 58-64. Again p. 69, seq., "There is the system of Constructive Idealism. It may be so called to distinguish it from the more developed and extreme Idealism presently to be spoken of. According to this system, we do not perceive the real external world immediately, but only mediately—that is, the objects which we take as the things actually perceived are not the real objects at all, but only vicarious assurances, representatives, or nuntii of real unknown objects. The hills, the rocks, the trees, the stars, all the choir of heaven and earth, are not, in any of their qualities, primary, secondary, or whatever we choose to call them, the actual existences out of us, but only the addresses of a 'something' to our physiology, or eductions by our physiology out of a 'something.' They are all Thoughts or Ideas, with only this peculiarity involved in them, that they will not rest in themselves, but compel a reference to objects out of self, with which, by some arrangement or other, they stand in relation. Difficult as this system may be to understand, and violently as it wrenches the popular common sense, it is yet the system into which the great majority of philosophers in all ages and countries hitherto are seen, more or less distinctly, to have been carried by their speculations. While the Natural Realists among philosophers have been very few, and even these have been Realists in a sense unintelligible to the popular mind, quite a host of philosophers have been Constructive Idealists. These might be farther subdivided according to particular variations in the form of their Idealism. Thus, there have been many Constructive Idealists who have regarded the objects rising to the mind in external perception, and taken to be representative of real unknown objects, as something more than modifications of the mind itself—as having their origin without. Among these have been reckoned Malebranche, Berkeley, Clarke, Sir Isaac Newton, Tucker, and possibly Locke. But there have been other Constructive Idealists, who have supposed the objects rising in the mind in external perception to be only modifications of the mind itself, but yet, by some arrangement, vicarious of real unknown objects, and intimating their existence. Among such have been reckoned Descartes, Leibnitz, Condillac, Kant, and most Platonists. The general name 'Idealists' it will be seen properly enough includes both the classes as distinct from the Natural Realists, inasmuch as both classes hold that what the mind is directly cognizant of in external perception is only ideas. But, inasmuch as these ideas are held by both classes, though under divers hypotheses, to refer to real existences beyond themselves, and distinct from the perceiving mind, the thinkers in question may also properly enough be called Realists or Dualists, though not 'Natural' Realists or Dualists. They occupy a midway place between the Natural Realists and the philosophers next to be mentioned.
"There is the system of Pure Idealism, which abolishes matter as a distinct or independent existence in any sense, and resolves it completely into mind. Though this system is named in the scheme, for the sake of symmetry, and as the exact antithesis to Materialism, it is difficult to cite representatives that could be certainly discriminated from the merely Constructive Idealists just mentioned on the one hand, and from the school of philosophers next following on the other. Fichte is, perhaps, the purest example." Ibid. pp. 69-72.
For perfect clearness we must put together two other passages from Professor Masson's interesting volume:—
"There is the system of Nihilism, or, as it may be better called, Non-Substantialism. According to this system, the Phænomenal Cosmos, whether regarded as consisting of two parallel successions of phænomena (Mind and Matter), or of only one (Mind or Matter), resolves itself, on analysis, into an absolute Nothingness,—mere appearances with no credible substratum of Reality; a play of phantasms in a void. If there have been no positive or dogmatic Nihilists, yet both Hume for one purpose, and Fichte for another, have propounded Nihilism as the ultimate issue of all reasoning that does not start with some à priori postulate." Masson, "Recent British Philosophy," p. 66.... If any one could assert "There is no Absolute," surely it might be the Nihilist, who has analysed away both Matter and Thought, and attenuated the Cosmos into vapour and non-significance. Yet, from the abyss of a speculatively reasoned Nihilism more void than Hume's, Fichte returned, by a convulsive act of soul,—which he termed faith—an intense, a burning, a blazing Ontologist. Ibid. p. 81."[125]
This is certainly an eloquent account of philosophic Idealism as it may in its various phases be represented to the world of general readers. It turns, as every such speculation must turn, on the great principle, that our Sensations are so many series of signs and symbols.[126] They may be preordained, and our apprehension of them innate;—they may be arbitrary, and their interpretation the work of man's intelligence. To decide this question, is to decide something as to the extent of their relativity; but will any one pronounce their information absolutely true?
At this point occurs a wide divergence between two great schools of Idealism—the Psychological, and the Theological thinkers. These schools inosculate in respect of some of their arguments, and of their objections against ordinary modes of thought. They disagree, however, in their aims—the ports at which they land themselves and their disciples.