958 



SCIENCE 



[N. S. Vol. XXIX. No. 755 



to point out again the psychological fallacy 

 involved. The dyne has been defended in 

 a recent discussion before the Eastern Asso- 

 ciation of Physics Teachers/ as follows: 



First it will be noticed that, as the units of the 

 system are logically derived from the fundamental 

 units, logical reasoning on the part of the pupils 

 will be required. Those educators who contend 

 that the chief work of the physics teacher is to 

 entertain and amuse will not accept this as an 

 argument. Others, however, will take delight in 

 the opportunity afforded for rapid-fire drill and 

 review. Question — What is a watt? Answer — 

 A watt is a unit of power and is equal to a joule 

 a second. Q. — What is a joule? A. — A joule is 

 a unit of work and is equal to ten million ergs. 

 Q. — What is an erg? A. — ^An erg is the C.G.S. 

 unit of work and is the work done by a force of 

 one dyne acting through one centimeter. These 

 questions can be continued until the pupil has 

 not only shown that he knows the definition of 

 the centimeter, the second and the gram mass, 

 but also that he has a knowledge of what work, 

 force, etc., themselves are. 



In reply to this let me point out that 

 reasoning with words which have no con- 

 crete content is useless and scholastic. A 

 student may jingle along words like watt, 

 joule, erg, dyne; but, without clear con- 

 cepts of the meanings of these terms, his 

 logical faculties get no more training than 

 if he were arguing how many devils can 

 dance on the point of a needle. As Mr. H. 

 Poineare has pointed out ("Essay on the 

 General Definitions of Mathematics") : 



What has been gained in rigor has been lost 

 in objectivity. It is by withdrawing from reality 

 that this perfect purity has been acquired. Dem- 

 onstrations are constructed by logic, but inven- 

 tions are made through intuition. To know how 

 to criticize is good; but to know how to create is 

 better. Logic tells us that on such and such a 

 path we are sure to meet no obstacles; but it does 

 not tell us which path leads to the goal. The 

 faculty that enables us to do this is intuition. 



Second : I know of no physics teachers 

 who think the work of the physics teacher 

 is to amuse ; unless possibly it be those who 



* Eeport of the fifty-second meeting of the E. A. 

 P. T., p. 13. 



keep their students loafing over quantita- 

 tive experiments from which the difficulties 

 have been removed, by logic or otherwise, 

 and which are therefore incapable of giving 

 "discipline" in the true sense defined 

 above. 



Third: The string of questions and an- 

 swers rims along very smoothly on paper — 

 almost as smoothly as The House that Jack 

 Built : This is the dog, that worried the cat, 

 that killed the rat, that ate the malt, that 

 lay in the house that Jack built. To my 

 thinking, this latter is far richer in thought 

 content to the student than is the string 

 about watts, joules, ergs. Such a string of 

 questions may surely be continued till the 

 student has learned the words that are sup- 

 posed to define the gram mass, but no 

 amount of questioning of this sort will ever 

 lead him to a scientific concept of mass, or 

 to a "knowledge of what work, force, etc., 

 themselves are." Physicists are agreed 

 that knowledge of this sort is useless, even 

 if it were attainable. Thus Poineare says 

 ("Science and Hypothesis," page 78) : 



Even though direct intuition made known to us 

 the real nature of force in itself, it would be in- 

 sufficient as a foundation for mechanics; it would 

 besides be wholly useless. What is of importance 

 is not to know what force is, but to know how to 

 measure it. 



Again (page 73) : 



When we say force is the cause of motion, we 

 talk metaphysics, and this definition, if one were 

 content with it, would be absolutely sterile. For 

 a definition to be of any use, it must teach us to 

 measure force; moreover that suffices; it is not 

 at all necessary that it teach us what force is 

 in itself, nor whether it is the cause of the effect 

 of motion. 



In like vein William James says:' 

 The term " energy " doesn't even pretend to 

 stand for anything " objective." It is only a way 

 of measuring the surface of phenomena so as to 

 string their changes on a simple formula. 



At this same meeting of the Eastern Asso- 

 ciation of Physics Teachers the present es- 

 " " Pragmatism," p. 216. 



