3 i4 SCIENCE PROGRESS 



religious animosity that was raised helped to attract notice, and the ultimate effect 

 on the national thought was enhanced. When the changes in the outlook, 

 brought about by a discovery, are more subtle, they become more difficult to trace ; 

 but I believe that such doctrines as the atomic theory, the conservation of energy, 

 and the electric theory of matter, have had an influence on the public mind reach- 

 ing well beyond the limits of scientific specialists. 



This is true to a still greater extent of the investigations which have led to 

 recent advances in medical science. The researches of Pasteur, Lister, and their 

 followers, are triumphs of science applied directly to the benefit of mankind ; but 

 I fancy that their hold on our imagination is mainly due to the new vista opened 

 out on the nature of disease, the marvellous workings of the lower forms of life, 

 and the almost human attributes of blood corpuscles, which have been disclosed. 



The effect on a community is only the summation of the effect on individuals, 

 and if we judge by individuals there can be little doubt that, except under the stress 

 of abnormal circumstances, pure knowledge has as great a hold upon the public 

 mind as the story of its applications. I learned that early in life, when a series 

 of public lectures was organised by the University of Manchester. The Professors 

 were asked to submit titles of lectures they were willing to give, and these were 

 submitted to Working Men's Clubs in Lancashire, who selected those they desired 

 to be delivered to them. Thinking that they would be more interested in matters 

 which affected their daily life, I drew up a list accordingly ; but for my own 

 satisfaction I included one on an astronomical subject : and that was the only one 

 ever chosen. Astronomy has a particular fascination, for the reason that it is, 

 perhaps, furthest removed from our ordinary concerns. During the most critical 

 period of the American Civil War, Abraham Lincoln used to seek refuge from his 

 worries and anxieties by spending his nights in the Observatory at Washington 

 watching the heavens. On a previous occasion I have already told the story of 

 the American politician who, during a Presidential Election in which he was 

 keenly interested, visited a friend who possessed a telescope. After an hour 

 spent in contemplation of the heavens, and having received answers to some of 

 his questions, he was silent for awhile, and then left the I'oora, saying : " It does 

 not matter after all whether Taft or Brian gets in." 



Not long ago I overheard — in a London club — a conversation between three 

 literary celebrities, who were discussing the relative merits of different studies. 

 One of them blamed scientific men, on the ground that they could not distinguish 

 between " evidence " and " proof. ' ; I confess I was startled, because I could not 

 imagine anyone to whom the distinction is more constantly brought home in his 

 daily work than the student of science. We speak of proving a statement when 

 we can show by correct reasoning that certain conclusions follow from certain 

 premises. It is a qualified proof, because the conclusions depend on the truth of 

 the premises. We have, in fact, only shown that the conclusion is contained in 

 the premises. It is the mathematician, and not the logician, who points out that 

 the propositions of Euclid need not be true, because we can imagine a space in 

 which the axioms on which they are based are not true. As regards the truth of 

 scientific theories, we do not pretend ever to reach an absolute proof. We can 

 accumulate evidence until it becomes so overpowering that all known alternatives 

 are excluded ; but I have never come across the scientific man who would not 

 admit that new alternatives may arise at some future time. My reason for 

 mentioning the incident is that I know how difficult it is for a sane man to make 

 any statement whatsoever that does not contain a grain of truth, and this grain is 

 often worth picking out. I find it in this case in a subsidiary effect possibly pro- 



