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.