84G 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



ON THE TEACHING OF NATURAL PHILOSOPHY. 1 



By Professor P. G. TAIT. 



AT the very outset of our work two questions 

 of great importance come prominently for- 

 ward. One of these, I have reason to conclude from 

 long experience, is probably a puzzling one to a 

 great many of you ; the other is of paramount con- 

 sequence to us all. And both are of consequence 

 not to us alone but to the whole country, in its 

 present feverish state of longing for what it but 

 vaguely understands and calls science-teaching. 

 These questions are, What is Natural Philosophy ? 

 and, How is it to be taught ? 



A few words only on the first question must 

 suffice for the present. The term Natural Phi- 

 losophy was employed by Newton to describe the 

 study of the powers of Nature : the investigation 

 of forces from the motion they produce, and the 

 application of the results to the explanation of 

 other phenomena. It is thus a subject to whose 

 proper discussion mathematical methods are in- 

 dispensable. The " Principia " commences with 

 a clear and simple statement of the fundamental 

 laws of motion, proceeds to develop their more 

 immediate consequences by a powerful mathe- 

 matical method of the author's own creation, and 

 extends them to the whole of what is now called 

 Physical Astronomy. And in the preface New- 

 ton obviously hints his belief that in time a sim- 

 ilar mode of explanation would be extended to 

 the other phenomena of external Nature. 



In many departments this has been done to a 

 remarkable extent during the two centuries which 

 have elapsed since the publication of the " Prin- 

 cipia." In others scarcely a single step of any 

 considerable magnitude has been taken ; and, in 

 consequence, the boundary between that which 

 is properly the subject of the natural philoso- 

 pher's inquiries and that which is altogether be- 

 yond his province is at present entirely indefinite. 

 There can be no doubt that, in many important 

 respects, even life itself is dependent upon pure- 

 ly physical conditions. The physiologists have 

 quite recently seized, for their own inquiries, a 

 great part of the natural philosopher's apparatus, 

 and with it his methods of experimenting. But 

 to say that even the very lowest form of life, not 

 to speak of its higher forms, still less of volition 



1 Extended from Notes of the Introductory Lect- 

 ure to the ordinary course of Natural Philosophy in 

 Edinbargh University, October 31, 1877. 



and consciousness, can be fully explained on phys- 

 ical principles alone — i. e., by the mere relative 

 motions and interactions of portions of inani- 

 mate matter, however refined and sublimated — is 

 simply unscientific. There is absolutely nothing 

 known in physical science which can lend the 

 slightest support to such an idea. In fact, it fol- 

 lows at once from the Laws of Motion that a ma- 

 terial system, left to itself, has a perfectly deter- 

 mined future, i. e., that upon its configuration 

 and motion at any instant depend all its sub- 

 sequent changes ; so that its whole history, 

 past and to come, is to be gathered from one al- 

 most instantaneous, if sufficiently comprehensive, 

 glance. In a purely material system there is 

 thus necessarily nothing of the nature of a free 

 agent. To suppose that life, even in its lowest 

 form, is wholly material, involves therefore either 

 a denial of the truth of Newton's laws of motion, 

 or an erroneous use of the term " matter." Both 

 are alike unscientific. 



Though the sphere of our inquiries extends 

 wherever matter is to be found, and is therefore 

 coextensive with the physical universe itself, 

 there are other things, not only without but with- 

 in that universe, with which our science has ab- 

 solutely no power to deal. In this room we sim- 

 ply recognize them, and pass on. 



Modern extensions of a very general state- 

 ment made by Newton enable us now to specify 

 much more definitely than was possible in his 

 time the range of physical science. We may now 

 call it the Science of Matter and Energy. These 

 are, as the whole work of the session will be de- 

 signed to prove to you, the two real things in the 

 physical universe; both unchangeable in amount, 

 but the one consisting of parts which preserve 

 their identity, while the other is manifested only 

 in the act of transformation, and though measu- 

 rable cannot be identified. I do not at present 

 enter on an exposition of the nature or laws of 

 either ; that exposition will come at the proper 

 time ; but the fact that so short and simple a defi- 

 nition is possible is extremely instructive, show- 

 ing, as it unquestionably does, what very great 

 advances physical science has made in recent 

 times. The definition, in fact, is but little infe- 

 rior in simplicity to two of those with which most 

 of you are no doubt already to a certain extent 



