But the scientific tendency in critical thought, tho 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 dye-stuffs; 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 bath-tub, 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. Common sense is the more CONSOLIDATED stage, because it got its innings first, and made all language into its ally. Whether it or science be the more AUGUST stage may be left to private judgment. But neither consolidation nor augustness are decisive marks of truth. If common sense were true, why should science have had to brand the secondary qualities, to which our world owes all its living interest, as false, and to invent an invisible world of points and curves and mathematical equations instead? Why should it have needed to transform causes and activities into laws of 'functional variation'? Vainly did scholasticism, common sense's college-trained younger sister, seek to stereotype the forms the human family had always talked with, to make them definite and fix them for eternity. Substantial forms (in other words our secondary qualities) hardly outlasted the year of our Lord 1600. People were already tired of them then; and Galileo, and Descartes, with his 'new philosophy,' gave them only a little later their coup de grace.
But now if the new kinds of scientific 'thing,' the corpuscular and etheric world, were essentially more 'true,' why should they have excited so much criticism within the body of science itself? Scientific logicians are saying on every hand that these entities and their determinations, however definitely conceived, should not be held for literally real. It is AS IF they existed; but in reality they are like co-ordinates or logarithms, only artificial short-cuts for taking us from one part to another of experience's flux. We can cipher fruitfully with them; they serve us wonderfully; but we must not be their dupes.
There is no RINGING conclusion possible when we compare these types of thinking, with a view to telling which is the more absolutely true. Their naturalness, their intellectual economy, their fruitfulness for practice, all start up as distinct tests of their veracity, and as a result we get confused. Common sense is BETTER for one sphere of life, science for another, philosophic criticism for a third; but whether either be TRUER absolutely, Heaven only knows. Just now, if I understand the matter rightly, we are witnessing a curious reversion to the common-sense way of looking at physical nature, in the philosophy of science favored by such men as Mach, Ostwald and Duhem. According to these teachers no hypothesis is truer than any other in the sense of being a more literal copy of reality. They are all but ways of talking on our part, to be compared solely from the point of view of their USE. The only literally true thing is REALITY; and the only reality we know is, for these logicians, sensible reality, the flux of our sensations and emotions as they pass. 'Energy' is the collective name (according to Ostwald) for the sensations just as they present themselves (the movement, heat, magnetic pull, or light, or whatever it may be) when they are measured in certain ways. So measuring them, we are enabled to describe the correlated changes which they show us, in formulas matchless for their simplicity and fruitfulness for human use. They are sovereign triumphs of economy in thought.
No one can fail to admire the 'energetic' philosophy. But the hypersensible entities, the corpuscles and vibrations, hold their own with most physicists and chemists, in spite of its appeal. It seems too economical to be all-sufficient. Profusion, not economy, may after all be reality's key-note.
I am dealing here with highly technical matters, hardly suitable for popular lecturing, and in which my own competence is small. All the better for my conclusion, however, which at this point is this. The whole notion of truth, which naturally and without reflexion we assume to mean the simple duplication by the mind of a ready-made and given reality, proves hard to understand clearly. There is no simple test available for adjudicating offhand between the divers types of thought that claim to possess it. Common sense, common science or corpuscular philosophy, ultra-critical science, or energetics, and critical or idealistic philosophy, all seem insufficiently true in some regard and leave some dissatisfaction. It is evident that the conflict of these so widely differing systems obliges us to overhaul the very idea of truth, for at present we have no definite notion of what the word may mean. I shall face that task in my next lecture, and will add but a few words, in finishing the present one.
There are only two points that I wish you to retain from the present lecture. The first one relates to common sense. We have seen reason to suspect it, to suspect that in spite of their being so venerable, of their being so universally used and built into the very structure of language, its categories may after all be only a collection of extraordinarily successful hypotheses (historically discovered or invented by single men, but gradually communicated, and used by everybody) by which our forefathers have from time immemorial unified and straightened the discontinuity of their immediate experiences, and put themselves into an equilibrium with the surface of nature so satisfactory for ordinary practical purposes that it certainly would have lasted forever, but for the excessive intellectual vivacity of Democritus, Archimedes, Galileo, Berkeley, and other excentric geniuses whom the example of such men inflamed. Retain, I pray you, this suspicion about common sense.
The other point is this. Ought not the existence of the various types of thinking which we have reviewed, each so splendid for certain purposes, yet all conflicting still, and neither one of them able to support a claim of absolute veracity, to awaken a presumption favorable to the pragmatistic view that all our theories are INSTRUMENTAL, are mental modes of ADAPTATION to reality, rather than revelations or gnostic answers to some divinely instituted world-enigma? I expressed this view as clearly as I could in the second of these lectures. Certainly the restlessness of the actual theoretic situation, the value for some purposes of each thought-level, and the inability of either to expel the others decisively, suggest this pragmatistic view, which I hope that the next lectures may soon make entirely convincing. May there not after all be a possible ambiguity in truth?