OBJECT OF NATURAL SCIENCR. "19 



as that of the nature of scientific certainty (stated in the second 

 principle), and that of the hmitation of scientific knowledge as 

 regards scope (third principle). 



This doctrine as to the logical form of all scientific asser- 

 tions seems to follow at once from the definition of science, as 

 st)on as we ask ourselves what sort of assertit)ns are thev which 

 observation and experiment serve to test. If a mere observa- 

 tion serves to test an assertion, to reveal it as true or false, it 

 can only be because the assertion, whatever its form, is an asser- 

 tic^n as to what would be the result of such an observation. 

 Consider again an experimental observation. This is an observa- 

 tion or inspection following on an operation of some sort, and 

 if a procedure like this tests an assertion, it can only be because 

 the assertion is a statement as to what would be observable as 

 the result of that oi)eration. The ])rinciple, therefore, as to the 

 nature of all scientific assertions is a mere translation into logical 

 terms of the conceptions of observation and experiment. 



Let me gi\e one or two very simple examples of the trans- 

 lation of statements from the technical language of science into 

 conditional promises expressed in ordinarv language. 



Consider the following two statements. (a) A point P 

 moves with constant velocity, (b) If a point P is initially at A, 

 and one second later at B. then at any other instant, say ii seconds 

 •c\iter passing" through A, it will be found in the position C, where 

 C is on A B and A C is ;; times A B. These two statements 

 are logically equivalent. Either may be deduced from the other 

 by processes of purely formal logic, once the logical definition 

 of the technical term velocity is known. The difference between 

 them is that one is expressed in highly technical scientific lan- 

 guage which hides its logical form, the other is expressed in 

 ordinary language which reveals its intention as a conditional 

 promise. 



Consider next the following pair of statements, (a) The 

 specific gravity of lead is 9.2. (b) Let a ])iece of lead be ap])lied 

 in any definite manner to a deformalile system, and let some read- 

 ing of this system taken in any definite manner be noted. Then if 

 we apply to the system in the same manner a quantity of standard 

 water whose volume is y.2 times that of the lead, the reading 

 l)roduced will be fcnnid to be the same as before. Here, again, 

 the two statements are logically equivalent, but the second is 

 of such a form that its logical intention as a conditional ])romise 

 is apparent. 



Now unfortunately a mere description of the philoso])hic 

 nature of science is inadequate as an answer to the more im- 

 portant question as to whether the influence of science on human 

 thinking has limits. The reason is that it may be doubted whether 

 all our knowledge is not in reality of the form " If you do so 

 and so, etc." It may be doubted, that is, whether all our know- 

 ledge is not scientific in form, and destined to actual conquest 

 by organised science. 



