.^oS 



NATURE 



[Aug. 15, 1872 



speaks as confidently of the Sun's Chromosphere of incan- 

 descent Hydrogen, and of the loral outbursts which cause 

 it to send forth projections tens of thouiiands of miles high, 

 as if he had been able to capture a llask of this gas, and 

 had generated water by causing it to unite with oxyjjen. 

 Yet this confidence is entirely based on the assumption 

 that a certain line which is seen in the Spectrum of 

 a hydrogen (lame nie:tns hydrogen also when seen in the spect- 

 rum of the Sun's chromosphere ; and high as is the probabililv of 

 that asiumption, it cannot be regarded as a dsmons'.rativa cer- 

 tainty, sincj it is by no m^ans incin.ceivable that the sime line 

 might be produced by some other substance at present unknown. 

 And so when Dr. Huggins deiluce^ from the different relative 

 positions of certain lines in the spectra of different Stars, that 

 these Stars are moving from or towards us in space, his admirable 

 train of reasoning is based on the assumption that these lines 

 have the same ineaains; — that is. that they represent the same 

 elements — in every luminary. That assumption, like the pre- 

 ceding, may be regarded as possessing a sufficiently high pro- 

 bability to jus'ify the reasoning based upon it ; more especially 

 since, by the other researches of that excellent observer, the same 

 Chemical elements have been detected as vapours in those filmy 

 cloudlets which seem to be stars in an early stage of consolida- 

 tion. But when Franklandand Lockyer, seeing in the spectrum 

 of the yellow Solar prominences a certain bright line not identi- 

 fiable with that of any known Terrestrial flame, attribute this to 

 a hypothetical new substance which they propose to call Helium, 

 it is obvious that tlieir assumption rests on a f^ir less secure 

 foundation ; until it shall have received that verification, which, 

 in the case of Mr. Crookes's researches on Thallium, was afforded 

 by the actual discovery of the new metal, whose presence had 

 been indicated by hinr by a line in the Spectrum not attributable 

 to any substance then known. 



In a large number of other cases, moreover, our Scientific 

 interpretations are c'early matters of judgment ; and this is 

 eminently a personal act, the value of its results depending in 

 each case upon the qualifications of the individual for arriving at 

 a correct decision. The surest of such judgments are those 

 dictated by what we term "Common Sense," as to matters on 

 which there seems no room for difference of opinion, because 

 every sane person comes to the same conclusion, although he may 

 be able to give no other reason for it than that it appears to him 

 " self evident." Thus while Philosophers have raised a thick 

 cloud of dust in the discussion of the basis of our b:lief in the 

 existence of the world external to ourselves — of the Non Ego, 

 as distinct from the Ego — and while every Logician claims to 

 have found some flaw in the proof advanced by every other — 

 the Common Sense of Mankind has arrived at a decision that is 

 practically worth all the arguments of all the Philosophers who 

 have fought again and again over this battle-ground. And I 

 think it can be shown that the trustworthiness of this Common 

 Sense decision arises from its dependence, not on any one set of 

 Experiments, but upon our unconscious co-ordination of the whole 

 aggregate of our Experiences— XiOl on the conclusiveness of any 

 one train of Reasoning, but on the convergence op all our lines of 

 thought to"ii'ards this one centre. 



Now this "Common Sense," disciplined and enlarged by 

 appropriate culture, becomes one of our most valuable instru- 

 ments of Scientific inquiry ; affording in many instances the best, 

 and sometimes the only, basis for a rational conclusion. Let us 

 take as a typical case, in which no special knowledge is required, 

 what we are accustomed to call the "flint implements" of the 

 Abbeville and Amiens gravel-beds. No logical proof can be 

 adduced that the peculiar shapes of these flints were given to 

 them by Human hands ; but does any unprejudiced person now 

 doubt it ? The evidence of design, to which, after an examina- 

 tion of one or two such specimens, we should only be justified in 

 attaching a probable value, derives an irresistible cogency from 

 accumulaiion. On the other hand, the /.-//probability that these 

 flints acquired their peculiar shape by accident, becomes to our 

 minds greater and greater as more and more such specimens are 

 found ; until at last this hypothesis, although it cannot be 

 directly disproved, is felt to be almost inconceivable, except liy 

 minds previously "possessed" by the "dominant idea" of the 

 modern origin of Man. And thus what was in the first instance 

 a matter of di.-cusjion, has now become one of those "self- 

 evident " propositions, which claim the unhesitating assent of all 

 whose opinion on the subject is entitled to the least weight. 



We proceed upwards, however, from such questions as the 

 Common Sense of Mankind generally is competent to decide, to 



those in which special knowledge is required to give value to the 

 judgment ; and thus the interpretation of Nature by the use of 

 that faculty comes to be more and more individual ; things being 

 perfectly "self-evident" to men of special culture, which ordi- 

 nary men, or men whose training has lain in a different direction, 

 do not apprehend as such. Of all departments of Science, 

 Geology seems to me to be the one that most depends on this 

 specially-trained "Common Sense;" which brings as it were 

 into one focus the light afforded by a great variety of studies — ■ 

 Physical and Chemical, Geographical and B.ological ; and 

 throws it on the pages of that Great Stone Book, on which the 

 past history of our Globe is recorded. And whilst Astrono.-ny is 

 of all Sciences that which may be coniidered as most nearly 

 representing Nature as she really is, Geology is that which most 

 completely represents her as seen through the medium of the 

 interpreting mind ; the meaning of the phenomena that constitute 

 its data being in almost every instance open to question, and the 

 judgments passed upon the same facts being often different 

 according to the qualifications of the several judges. No one 

 who has even a general acquaintance with the history of this 

 department of Science, can fail to see that the Geology of each 

 epoch has been the reflection of the Minds by whica its stu ly 

 was then directed ; and that its true progress dates from the time 

 when that "Common Sense" method of interpretation came 

 to be ^£'//tV(7/ V adopted, which consists in seeking the explana- 

 tion of past changes in the Forces at present in operation, 

 instead of invoking the aid of extraordinary and mysterious 

 agencies, as the older Geologists were wont to do, whenever 

 they wanted — like the Ptolemaic Astronomers — " to save appear- 

 ances." The whole tendency of the ever-widening range of 

 modern Geological inquiry has been to show how little reliance 

 can be placed upon the so-called "Laws" of Stratigraphical 

 and Pateontological Succession, and how much allowance has to 

 be made for local conditions. .So that while the Astronomer is 

 constantly enabled to point to the fulfilment of his predictions as 

 an evidence of the correctness of his method, the Geologist is 

 almost entirely destitute of any such means of verification. For 

 the value of any prediction that he may hazard — as in regard to 

 the existence or non-existence of Coal in any given area — de- 

 pends not only upon the truth of the general doctrines of Geo- 

 logy in regard to the succession of Stratified Deposits, but still 

 more upon the detailed knowledge which he may have acquired 

 of the distribution of those Deposits in the particular locality. 

 Hence no reasonably-judging man would discredit either the 

 general doctrines or the methods of Geology, because the pre- 

 diction proves untrue in svtch a case as that now about to be . 

 brought in this neighbourhood to the trial of experience. 



We have thus considered Man's function as the Scientific In- 

 terpreter of Nature in two departments of Natural Knowledge ; 

 one of which affords an example of the strictest, and the other 

 of the freest method, which Man can employ in constructing his 

 Intellectual representation of the Universe. And as it would 

 be found that in the study of all other departments the same 

 methods are used, either separately or in combination, we may 

 pa5S at once to the other side of our inquiry, namely, the origin 

 of those Primary Beliefs which constitute the groundwork of all 

 Scientific reasoning. 



The whole fabric of Geometry rests upon certain Axioms 

 which every one accepts as true, but of which it is necessary that 

 the truth should be assumed, because they are incapable of de- 

 monstration. So, too, the deliverances of our " Common 

 Sense " derive their trustworthiness from what we consider the 

 "self-evidence" of the propositions affirmed. 



This inquiry brings us face to face with one of the great Philo- 

 sophical problems of our day, which has been discu sed by 

 Logicians and Metaphysicians of the very highest ability as 

 Leaders of opposing Schools, with the one result of showing 

 how ranch can be said on each side. By the Intuitionalists it 

 is asserted that the tendency to form these Primary Beliefs is in- 

 born in Man, an original part of his mental organisation ; so 

 that they grow up spontaneously in his Mind as its faculties are 

 gradually unfolded and developed, requiring no other Experi- 

 ence for their genesis, than that which suffices to call these 

 faculties into exercise. But by the advocates of the doctrine 

 which regards v^Tj-Ztv/W/ri? as the basis of all our knowledge, it is 

 maintained that the Primary Beliefs of each individual are 

 nothing else than generalisations which he formed of such 

 expeiiencrs as he has ei'her himself acquired or has consciously 

 learned from others ; and they deny that there is any original or 

 intuitive tendency to the formation of such bches, beyond 



