84 £SSAVS IN PHILOSOPHY 



by unquestionable presence in sensible experience. 

 All the refinements of scientific method — the pre- 

 cautions of repeated observation, the probing subtle- 

 ties of experiment, the niceties in the use of 

 instruments of precision, the principle of reduction 

 to mean or average, the allowing for the " personal 

 equation," the final casting out of the largest mean 

 of possible errors in experiment or observation, by 

 such methods, for instance, as that of least squares 

 — all these refinements are for the single purpose of 

 making it certain that our basis of evidence shall be 

 confined to what has actually been present in the 

 world of sense. We are to know beyond question 

 that such and such conjunctions of events have 

 actually been present to the senses, and precisely 

 what it is that thus remains indisputable fact after 

 all possible additions or misconstructions of our mere 

 thought or fancy have been cancelled out. Such 

 conjunctions in unquestionable experience, isolated 

 and then purified from foreign admixture by care- 

 fully contrived experiment, we are finally to raise by 

 generalisation into a tentative expectation of their 

 continued recurrence in the future ; tentative expec- 

 tation, we say, because the empirical method in its 

 rigour warns us that the act of generalisation is a 

 step beyond the strict evidence, and must not be 

 reckoned any part of science except as it continues 

 to be verified in subsequent experience of the event 



