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��of the use of axioius appears, acc-oi'diog to our author, in the fact that ihe learner, from long habit- (not, as Mach thinks, from any a priori insight), has come to expect instinctively, and ao to conceive very economically, certain simple sequences of facts. I'urely for economic rea- sons, and not on philosophic grounds, nor for that matter with any philosophic justifleation, the teacher is disposed to seize upon these ele- mentary facts as the constituents into which more complex facts can be analyzed, and b}' which these cases can be easily described. These simpler sequences are chosen simply because the learner already knows of them, and can more readily grasp them. When one calls them a priori, one forgets how easily a puzzling question can confuse us about their meaning, and even about their truth. Their self-evidence is the self-evidence of instinct, and thej' are in no philosophical sense a priori.

After the foregoing summary, we may fairly assert that in one respect, at any rate, Mach's method is praiseworthy; and that is, in its tendency to get rid of the mysterious element of his science. Whatever one maj' hold about the a priori in general, there is no doubt that we have had enough and too much of the purely mystical a priori. If there is any fundamental rational truth at the bottom of science, if science is more than a mere aggre- gation of facts, this rational basis, when we come to state it, must be as frank and honest and manly a principle as the most common- place adherent of the empirical philosophy could desire. The old-fashioned a priori, in science, in morals, in religion, used to be represented as an arrogant aud intolerant thing, mjsterious iu its manner of speech, violent and dogmatic in its defence of its own claims. The English empiricists used to hate this aristocratic a priori, and they shrewdly suspected it to be a humbug. What they gave us in its place, however, was a vague and unphilosophic doctrine of science, that you could only seem to understand, so long as you did not examine ioto its meaning.

Mach's view avoids the mj'stery of the old a priori. He leaves us still the mystery of the correspondence of external nature to our fun- damental interests in the simplicity of its phe- nomena. Yet this mystery has the look of the genuine philosophic problem. The new empir- icism is not and can not be final ; but it prom- ises to prove an excellent beginning, and one can at least commend it to those instructors in elementary mechanics who still puzzle their pupils with their use of the old-fashioned, mystical a priori. Mach's fundamental prin-

��ciple of the economy of thought is one Uut any intelligent pupil, with a few empirical facts before him, could be got to uuderstand. But, aa many not extraordinarily stupid pupils hai-e so often felt, the mysterious waj' in wlueh such axioms as the ' principle of sufGcient reason ' used to appear, aimlessly wandering to and fro in the test^books, could not but per- plex, without in any wise helping, the young mind. That even to-day. when the empirical methods in elementary mechanics are so well developed and so generally used, the ' princi- ple of suSieient reason ' is occasionally caltetl in to help teachers and text-books out of dif- ficult places, — this fact is surely a ' sufficient reason ' in itself for a careful study of such books as Mach's. There are many teachers of elementary mechanics to-day, who, while abhorring metaphjsics, and constantly glorify- ing experience, never know or can tell jnal what ought to be done with that ' principle of sufficient reason,' which, however, as it used to be applied when it held sway in elementary mechanics, was the most miserably ' metaphys- ical ' of all confused statements. The moat ardent believer in the rational a priori must therefore delight to find, in such a book as Mach's, the foundation laid for future philo- sophic inquiry iu the clear and sensible empiri- cism of the author, tentative and transient though this doctrine itself may prove. Only when the vague and mystical have been ban- ished from the mere terms and axioms of the science, can a philosophic student ho|>e suc- cessfully to grapple with the questioi is empirical science, with certain and fixej results, possible at all ? " Every one is Iher fore interested in such undertakings as ( author's, whether one is student of mechaid or of logic, or teacher of either ; for every o is interested in plain and frank thinking, f from appeals to merel}- mystical principles.

In concluding, we must call special attentit to our author's discussion of the question d absolute and relative motion, which he se to us to have treated with maii'ellous skill ; thus we are obliged unwilhngly to leave that is so full of learning and su^estion.

THE SNAKE-DANCE OP THE M0«P/4|

Capt. Bourkk has given us here a most fi teresting account of his experience among ti

o( . *ou7n% ft" lloqul iBdIUis < ■ndouiMmiofl ing «U||1bii. rlL. u^n third U.S.

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