July 21, 1892] 



NA TURE 



269 



cwo of these conditions. He has not yet said that I ought also 

 to have discussed the impossible dynamics in which the third 

 condition would be violated. 



This, however, was not his original position. He began (see 

 his original article, Nature, April 28, p. 607) by supposing 

 that a motion from which light emanated cannot, if non-periodic, 

 be investigated by Fourier's theorem ; and he stated that in con- 

 sequence of this he could not understand the decomposition of 

 the motion of an electron within a molecule into a series of 

 superposed elliptic motions. In Nature for May 12, p. 29, 

 and for June 9, p. 126, I demonstrated in two different ways 

 that his supposition was a mistake. The other objection made 

 in his original article, viz. that "a plausible suggestion about 

 the movement of the molecules ought to explain more," is also 

 a mistake. These are the two condemnations passed on my 

 paper in his original article. Both these have been met. And 

 the issues he has since laised are, I again submit, not legitimate 

 criticism of a physical inquiry. To make them legitimate he 

 would need to produce an instance of a motion of the kind with 

 7uhich my paper deals {i.e. a motion that can produce a spectrum) 

 and which at the same time is not amenable to the method of 

 analysis given in chapter iv. of my memoir. This he cannot 

 do, for there are no such motions. In fact, the analysis effected 

 by the spectroscope is identical with a part of that made by 

 Fourier's theorem when applied in the way that I there point 

 out. The spectroscope gives the periodic times in the different 

 partials, the sum of the squares of their principal axes, and in 

 some cases their forms ; but it does not give the phases of the 

 motions in them or the planes in which they lie. Prof. Runge 

 almost admits that his criticisms do not succeed in impugning 

 the value of my memoir as a contribution towards our know- 

 ledge of nature, for in his last letter he says, " I do not say, 

 therefore, that Prof. Stoney's views on the cause of the line- 

 spectra are wrong." This is very different from what he said 

 in April. G. Johnstone Stoney. 



9, Palmerston Park, Dublin, 

 July 17. 



"The Grammar of Science." 



May I, through your columns, point out to Prof. Pearson 

 what seems to me a serious " antinomy," to use his own phrase, 

 in his "Grammar of Science." The foundation of the whole 

 book is the proposition that since we cannot directly apprehend 

 anything but sense-impressions, therefore the things we com- 

 monly speak of as objective, or external to ourselves, and their 

 variations, are nothing but groups of sense-impressions and 

 sequences of such groups. But Prof. Pearson admits the exist- I 

 ence of other consciousnesses than his own, not only by im- > 

 plication in addressing his book to them, but explicitly in many | 

 passages. He says (p. 59): "Another man's consciousness, 

 however, can never, it is said, be directly perceived by sense- i 

 impression ; I can only infer its existence from the apparent i 

 similarity of our nervous systems, from observing the same 

 hesitation in his case as in my own between sense-impression 

 and exertion, and from the similarity between his activities and \ 

 my own." • 



With respect to the argument from the " similarity of our 

 nervous systems," I may point out, en passant, that however | 

 many other people's nervous systems Prof. Pearson may have I 

 dissected, he has certainly never dissected his own, and that i 

 therefore this argument, which is several times repeated in the i 

 book, is worthless ; all Prof. Pearson has to go upon is the ex- ' 

 ternal similarity of other people's bodies and activities to his ; 

 own. But he maintains that our bodies and their activities are 

 nothing but groups and sequences of sense- impressions. Con- | 

 sequently, if other consciousnesses are similar to his own, some j 

 of his groups of sense-impressions possess private conscious- I 

 nesses, which themselves receive sense-impressions, among 

 which, for example, are to be found Prof. Pearson himself! 

 Thus Prof Pearson's consciousness contains a number of parts, 

 each of which contains, amongst other things, Prof. Pearson 

 and his consciousness I Of course it would be impossible thus 

 to refute a consistent idealist, who maintained that not only ex- 

 ternal things but all other consciousnesses were unreal and 

 existed only in his imagination ; but to recognize the reality of 

 other consciousnesses is to recognize the reality of the means by 

 which we become aware of them, which, as Prof. Pearson ex- 

 plicitly states, is the external aspect of men's bodies. 



NO. II 86, VOL. 46] 



It is not difficult to find the way out of this difficulty. It is 

 that, though we do not inow, i.e. directly apprehend, anything 

 about the external world but sense-impressions, yet in order to 

 explain those impressions we frame the hypotheses of external, 

 objective reality, and of the " ejective " reality of other con- 

 sciousnesses, and since these hypotheses are successful in ex- 

 plaining most of our sense-impressions, we have come to believe 

 that they are true. Indeed, I cannot seriously doubt that Prof. 

 Pearson himself believes in them as much as anyone else. 

 Only, if he were to acknowledge it explicitly, he would have to 

 rewrite almost every page of "The Grammar of Science." 



Edward T. Dixon. 



12 Barkston Mansions, South Kensington, 

 July 14. 



Prof. Karl Pearson's " Grammar" merits more justice than 

 it has received from "C. G. K." It is a remarkable book 

 which I have read with much interest. He tells us (p. 15) that 

 " the unity of science consists alone in its method, not in its 

 material," and therefore the method employed in this work on 

 science acquires a special interest. 



There are two points in respect to which his method seems 

 to me to call for a few remarks — remarks which cannot be un- 

 welcome, since his motto is "La critique est la vie de la 

 science." 



The first point concerns his own position and that of certain 

 persons he freely criticizes. The Professor has scant patience 

 with metaphysics, and says not a few hard things of those tire- 

 some people the metaphysicians ; and yet his own book is really 

 a metaphysical treatise and he turns out himself to be an un- 

 conscious metaphysician malgre lui. This fact can hardly sur- 

 prise anyone who has mastered what is really the scientific 

 ABC; but in the present instance it is peculiarly amusing. 

 For he, with great naivete, ridicules Prof. Tait for being in the 

 very same case. He is styled (p. 296) " the unconscious meta- 

 physician, who groups sense-impressions and supposes them to 

 flow as properties from something beyond the sphere of percep- 

 tion"; and we are further told that " the unconscious meta- 

 physics of Prof. Tait occur on nearly every page of his treat- 

 ment of the fundamental concepts of physical science." 



The second point which seems to require notice is the way in 

 which his method plays "fast and loose " both with the system 

 he upholds and the system he most opposes. 



He is an idealist of a kind. Again and again we are told 

 that scientific laws are but descriptions of our feelings in con- 

 ceptual shorthand. He speaks (p. 129) of "the whole of 

 ordered ■a.zX.^x^" being " seen as the product of one mind — the 

 only mind with which we are acquainted," and he tells us plainly 

 (p. 130) that "the mind is absolutely confined within its nerve- 

 exchange ; beyond the walls of sense-impression it can logically 

 infer nothing." It would be easy to multiply such quotations. 



Now, of course the idealist can logically make use of ordinary 

 language in describing co-existences and successions between his 

 feelings. The Professor's distinctions (p. 1 14) between " physical 

 and metaphysical supersensuousness " have been duly noted, as 

 also his disclaimer (p. 57) of giving any real explanation of the 

 physical side of thought. Nevertheless, none of these considera- 

 tions appear to me to justify his dogmatic mode of speaking of 

 things of which the senses can take no cognizance. 



If he knows nothing but his own feelings, he cannot rea'^on- 

 ably speak of their mode of formation, or of the manner in 

 which one group of feelings acts upon another. Yet, referring 

 to a sensory nerve, he writes (p. 51) : "The manner [the italics 

 are mine] in which this nerve conveys its message is, without 

 doubt, physical," and (p. 81) " Beyond the brain terminals of 

 the sensory nerves we cannot get." Stars are for him but 

 "groups of feelings," and yet he writes about them as follows : 

 " Among the myriad pl.anetary systems we see on a clear night, 

 there surely must be myriad planets which have reached our own 

 stage of development, and teem, or have teemed, with human 

 life" (p. 179). 



Speaking of waves (p. 305) he tells us, "The yiSiVQ forms lot 

 us a group of sense-impressions." But the wave is, for him, 

 itself z. group of self-impressions and so is a particle of proto- 

 plasm. Nevertheless he speaks (p. 413) of the probability that 

 long stages of development preceded its existence, and "of the 

 millions of years, with complex and varying conditions of tem- 

 perature," needed in order "to pass from the chemical substance 

 of life to that complex structure which may have been the first 



