For all utilitarian practical purposes these conceptions amply suffice; but that they began at special points of discovery and only gradually spread from one thing to another, seems proved by the exceedingly dubious limits of their application today. We assume for certain purposes one “objective” Time that aequabiliter fluit, but we don’t livingly believe in or realize any such equally-flowing time. “Space” is a less vague notion; but “things,” what are they? Is a constellation properly a thing? or an army? or is an ens rationis such as space or justice a thing? Is a knife whose handle and blade are changed the “same”? Is the “changeling,” whom Locke so seriously discusses, of the human “kind”? Is “telepathy” a “fancy” or a “fact”? The moment you pass beyond the practical use of these categories (a use usually suggested sufficiently by the circumstances of the special case) to a merely curious or speculative way of thinking, you find it impossible to say within just what limits of fact any one of them shall apply.
The peripatetic philosophy, obeying rationalist propensities, has tried to eternalize the commonsense categories by treating them very technically and articulately. A “thing” for instance is a being, or ens. An ens is a subject in which qualities “inhere.” A subject is a substance. Substances are of kinds, and kinds are definite in number, and discrete. These distinctions are fundamental and eternal. As terms of discourse they are indeed magnificently useful, but what they mean, apart from their use in steering our discourse to profitable issues, does not appear. If you ask a scholastic philosopher what a substance may be in itself, apart from its being the support of attributes, he simply says that your intellect knows perfectly what the word means.
But what the intellect knows clearly is only the word itself and its steering function. So it comes about that intellects sibi permissi, intellects only curious and idle, have forsaken the commonsense level for what in general terms may be called the “critical” level of thought. Not merely such intellects either—your Humes and Berkeleys and Hegels; but practical observers of facts, your Galileos, Daltons, Faradays, have found it impossible to treat the naifs sense-termini of common sense as ultimately real. As common sense interpolates her constant “things” between our intermittent sensations, so science extrapolates her world of “primary” qualities, her atoms, her ether, her magnetic fields, and the like, beyond the commonsense world. The “things” are now invisible impalpable things; and the old visible commonsense things are supposed to result from the mixture of these invisibles. Or else the whole naif conception of thing gets superseded, and a thing’s name is interpreted as denoting only the law or regel der verbindung by which certain of our sensations habitually succeed or coexist.
Science and critical philosophy thus burst the bounds of common sense. With science naif realism ceases: “Secondary” qualities become unreal; primary ones alone remain. With critical philosophy, havoc is made of everything. The commonsense categories one and all cease to represent anything in the way of being; they are but sublime tricks of human thought, our ways of escaping bewilderment in the midst of sensation’s irremediable flow.
But the scientific tendency in critical thought, though inspired at first by purely intellectual motives, has opened an entirely unexpected range of practical utilities to our astonished view. Galileo gave us accurate clocks and accurate artillery-practice; the chemists flood us with new medicines and dyestuffs; Ampere and Faraday have endowed us with the New York subway and with Marconi telegrams. The hypothetical things that such men have invented, defined as they have defined them, are showing an extraordinary fertility in consequences verifiable by sense. Our logic can deduce from them a consequence due under certain conditions, we can then bring about the conditions, and presto, the consequence is there before our eyes. The scope of the practical control of nature newly put into our hand by scientific ways of thinking vastly exceeds the scope of the old control grounded on common sense. Its rate of increase accelerates so that no one can trace the limit; one may even fear that the being of man may be crushed by his own powers, that his fixed nature as an organism may not prove adequate to stand the strain of the ever increasingly tremendous functions, almost divine creative functions, which his intellect will more and more enable him to wield. He may drown in his wealth like a child in a bathtub, who has turned on the water and who cannot turn it off.
The philosophic stage of criticism, much more thorough in its negations than the scientific stage, so far gives us no new range of practical power. Locke, Hume, Berkeley, Kant, Hegel, have all been utterly sterile, so far as shedding any light on the details of nature goes, and I can think of no invention or discovery that can be directly traced to anything in their peculiar thought, for neither with Berkeley’s tar-water nor with Kant’s nebular hypothesis had their respective philosophic tenets anything to do. The satisfactions they yield to their disciples are intellectual, not practical; and even then we have to confess that there is a large minus-side to the account.
There are thus at least three well-characterized levels, stages or types of thought about the world we live in, and the notions of one stage have one kind of merit, those of another stage another kind. It is impossible, however, to say that any stage as yet in sight is absolutely more true than any other.
