370 



NA TURE 



[August 17, 1905 



point of view has been so far-reaching as almost to justify 

 the misapprehension of the unscientific as to the date 

 when the doctrines of evolution first originated in the mind 

 of man. 



It is not my object, nor indeed am I competent, to 

 examine the extent to which the theory of natural selection 

 has needed modification since it was first formulated by 

 my father and Wallace. But I am surely justified in 

 maintaining that the general principle holds its place firmly 

 as a permanent acquisition to modes of thought. 



Evolutionary doctrines concerning inanimate nature, 

 although of much older date than those which concern life, 

 have been profoundly affected by the great impulse of 

 which I have spoken. It has thus come about that the 

 origin and history of the chemical elements and of stellar 

 systems now occupy a far larger space in the scientific 

 mind than was formerly the case. The subject which I 

 shall discuss to-night is the extent to which ideas, parallel 

 "to those which have done so much towards elucidating 

 the problems of life, hold good also in the world of 

 matter ; and I believe that it will be possible to show that 

 in this respect there exists a resemblance between the two 

 realms of nature, which is not merely fanciful. It is 

 proper to add that so long ago as 1873 Baron Karl du Prel 

 ■discussed the same subject from a similar point of view, in 

 a book entitled " The Struggle for Life in the Heavens."' 



Although inanimate matter moves under the action of 

 forces which are incomparably simpler than those govern- 

 ing living beings, yet the problems of the physicist and 

 •the astronomer are scarcely less complex than those which 

 Tjresent themselves to the biologist. The mystery of life 

 remains as impenetrable as ever, and in his evolutionary 

 speculations the biologist does not attempt to explain life 

 itself, but, adopting as his unit the animal as a whole, 

 discusses its relationships to other animals and to the 

 surrounding conditions. The physicist, on the other hand, 

 is irresistibly impelled to form theories as to the intimate 

 constitution of the ultimate parts of matter, and he desires 

 further to piece together the past histories and the future 

 •fates of planets, stars, and nebulae. If then the specula- 

 •tions of the physicist seem in some respects less advanced 

 than those of the biologist, it is chiefly because he is more 

 ambitious in his aims. Physicists and astronomers have 

 not yet found their Johannesburg or Kimberley ; but 

 although we are still mere prospectors, I am proposing to 

 show you some of the dust and diamonds which we have 

 already extracted from our surface mines. 



The fundamental idea in the theory of natural selection 

 is the persistence of those types of life which are adapted 

 to their surrounding conditions, and the elimination by 

 extermination of ill-adapted types. The struggle for life 

 amongst forms possessing a ' greater or less degree of 

 adaptation to slowly varying conditions is held to explain 

 the gradual transmutation of species. Although a different 

 phraseology is used when we speak of the physical world, 

 yet the idea is essentially the same. 



The point of view from which I wish vou to consider 

 the^ phenomena of the world of matter m'av be best ex- 

 plained if, in the first instance, I refer to political institu- 

 tions, because we all understand, or fancy we understand, 

 .something of politics, whilst the problerris of physics are 

 commonly far less familiar to us. This illustration will 

 have a further advantage in that it will not be a mere 

 parable, but will involve the fundamental conception of 

 the nature of evolution. 



The complex interactions of man with man in a com- 

 munity are usually described by such comprehensive terms 

 as the State, the Commonwealth, or the Government. 

 Various States differ widely in their constitution and in 

 the degree of the complexity of their organisation, and 

 we classify them by various general terms, such as auto- 

 cracy, aristocracy, or democracy, which express somewhat 

 loosely their leading characteristics. But, for the purpose 

 of showing the analogy with phvsics, we need terms of 

 wider import than those habitually used in politics. All 

 forms of the State imply inter-relationship in the actions 

 of men, and action implies movement. Thus the State- 

 may be described as a configuration or arrangement of a 

 community of men; or we may say that it implies a 



1 "'D-r Kampf urn's Dasein am Himmel.' 7.\ 

 ^enicke, i?76.) 



Auflagf. (Berlin ; 



N 



O. 1868, VOL. 72] 



definite mode of motion of man — that is to say, an organ- 

 ised scheme of action of man on man. Political history 

 gives an account of the gradual changes in such con- 

 figurations or modes of motion of men as have possessed 

 the quality of persistence or of stability to resist the 

 disintegrating influence of surrounding circumstances. 



In the world of life the naturalist describes those forms 

 which persist as species; similarly the physicist speaks of 

 stable configurations or modes of motion of matter ; and 

 the politician speaks of States. The idea at the base of 

 all these conceptions is that of stability, or the power of 

 resisting disintegration. In other words, the degree of 

 persistence or permanence of a species, of a configuration 

 of matter, or of a State depends on the perfection of its 

 adaptation to its surrounding conditions. 



If we trace the history of a State we find the degree 

 of its stability gradually changing, slowly rising to a 

 maximum, and then slowly declining. When it falls to 

 nothing a revolution ensues, and a new form of govern- 

 ment is established. The new mode of motion or govern- 

 ment has at first but slight stability, but it gradually 

 acquires strength and permanence, until in its turn the 

 slow decay of stability leads on to a new revolution. 



Such crises in political history may give rise to a con- 

 dition in which the State is incapable of perpetuation by 

 transformation. This occurs when a savage tribe nearly 

 exterminates another tribe and leads the few survivors 

 into slavery ; the previous form of government then 

 becomes extinct. 



The physicist, like the biologist and the historian, 

 watches the effect of slowly varying external conditions ; 

 he sees the quality of persistence or stability gradually 

 decaying until it vanishes, when there ensues what is 

 called, in politics, a revolution. 



These considerations lead me to express a doubt whether 

 biologists have been correct in looking for continuous trans- 

 formation of species. Judging by analogy, we should 

 rather expect to find slight continuous changes occurring 

 during a long period of time, followed by a somewhat 

 sudden transformation into a new species, or by rapid 

 extinction. However this may be, when the stability of a 

 mode of motion vanishes, the physicist either finds that 

 it is replaced by a new persistent type of motion adapted 

 to the changed conditions, or perhaps that no such trans- 

 formation is possible, and that the mode of motion has 

 become extinct. The evanescent type of animal life has 

 often been preserved for us, fossilised in geological strata ; 

 the evanescent form of government is preserved in written 

 records or in the customs of savage tribes ; but the 

 physicist has to pursue his investigations without such 

 useful hints as to the past. 



The time-scale in the transmutation of species of animals 

 is furnished by the geological record, although it is not 

 possible to translate that record into years. As we shall 

 see hereafter, the time needed for a change of type in 

 atoms or molecules may be measured by millionths of a 

 second, while in the history of the stars continuous changes 

 may occupy millions of years. Notwithstanding this 

 gigantic contrast in speed, yet the process involved seems 

 to be essentially the same. 



It is hardly too much to assert that, if the conditions 

 which determine stability of motion could be accurately 

 formulated throughout the universe, the past history of 

 the cosmos and its future fate would be unfolded. How 

 indefinitely far we stand removed from such a state of 

 knowledge will become abundantly clear from the re- 

 mainder of my address. 



The study of stability and instability then furnishes 

 the problems which the physicist and biologist alike 

 attempt to .solve. The two classes of problems differ prin- 

 cipally in the fact that the conditions of the world of 

 life are so incomparably more intricate than those of the 

 world of matter that the biologist is compelled to abandon 

 the attempt to determine the absolute amount of the 

 influence of the various causes which have affected the 

 existence of species. His conclusions are merely quali- 

 tative and general, and he is almost universally compelled 

 to refrain from asserting even in general terms what are 

 the reasons which have rendered one form of animal life 

 stable and persistent, and another unstable and evanescent. 



On the other hand, the physicist, as a general rule. 



