RECENT ADVANCES IN SCIENCE 535 



to them just that kind of prima facie absurdity which would 

 naturally commend it to their belief. 



The apparent absurdity, however, is due merely to un- 

 familiarity. An uncultivated person finds it hard enough to 

 believe that the earth, apparently so still and solid, is really 

 in rapid motion, on its own axis, round the sun, and also with the 

 rest of the solar system in a straight line through space. If 

 there were no outside standard of comparison, the notion of 

 itself would be exceedingly difficult to grasp. The earth would 

 be regarded in all matters as the general standard of rest ; 

 movement would always mean movement relative to the earth, 

 and in the absence of any wider conception, movement would 

 thus appear to have an absolute value. So it now is with 

 regard to space and time. The only standard of space and time 

 hitherto known to us has been that prevalent on the earth ; 

 and accordingly they have appeared to be absolute and universal 

 in nature. But at length an outside standard of comparison 

 has been discovered ; and it is seen that our ideas of space and 

 time, formed by experience of the space and time upon the 

 earth, are no more absolute than are the ideas of motion which we 

 form by regarding the earth as motionless. We move yet a step 

 further from the anthropocentricity of primitive thought, where 

 everything is judged by the standards of our own immediate 

 outlook. We, after all, are not the centre of the universe ; our 

 earth is not the standard of absolute rest ; nor are our own 

 space and time absolute properties of the entire universe. 



The Principle of Relativity seems, therefore, to be in no way 

 opposed to the spirit of science as hitherto conceived. On the 

 contrary, it brings powerful reinforcement to the doctrine of the 

 Uniformity of Law, and the invariability of the laws of nature. 

 As stated in its most generalised form, the Principle of Rela- 

 tivity reads thus : " Given different groups of observers, some 

 of whom are in uniform motion of translation with reference 

 to others, the laws of nature are precisely identical for these 

 different groups of observers." By pre-relativity standards, 

 the laws of nature must have appeared different from these 

 different aspects ; a circumstance which might have afforded 

 some points of vantage to critics of scientific materialism, but 

 which appears to have escaped their attention. 



A few words must be said of the death of Prof. Ernst Haeckel, 

 which took place on August 8, 191 9. He passed, as many 

 others have done, from medicine to zoology, from zoology to 

 philosophy, and from philosophy to discussion of religious 

 problems ; and it is now largely with regard to the latter 

 spheres that he is remembered. The chief influence on his 

 life was probably his reading of the Origin of Species in i860. 

 He was an immediate convert, and set about to popularise the 



