SCIENTIFIC INVESTIGATION 87 



you have performed the operation of induction. You 

 found that, in two experiences, hardness and greenness 

 in apples went together with sourness. It was so in the 

 first case, and it was confirmed by the second. True, it 

 is a very small basis, but still it is enough to make an 

 induction from; you generalise the facts, and you ex- 

 pect to find sourness in apples where you get hardness 

 and greenness. You found upon that a general law 

 that all hard and green apples are sour; and that, so 

 far as it goes, is a perfect induction. Well, having got 

 your natural law in this way, when you are offered an- 

 other apple which you find is hard and green, you say, 

 "All hard and green apples are sour; this apple is hard 

 and green, therefore this apple is sour." That train of 

 reasoning is what logicians call a syllogism, and has all 

 its various parts and terms, its major premiss, its 

 minor premiss and its conclusion. And, by the help of 

 further reasoning, which, if drawn out, would have to 

 be exhibited in two or three other syllogisms, you arrive 

 at your final determination, "I will not have that ap- 

 ple." So that, you see, you have, in the first place, 

 established a law by induction, and upon that you 

 have founded a deduction, and reasoned out the special 

 particular case. Well now, suppose, having got your 

 conclusion of the law, that at some time afterwards, 

 you are discussing the qualities of apples with a friend : 

 you will say to him, " It is a very curious thing, but 

 I find that all hard and green apples are sour ! " Your 

 friend says to you, " But how do you know that ?" You 

 at once reply, "Oh, because I have tried them over 

 and over again, and have always found them to be 

 so." Well, if we were talking science instead of com- 

 mon sense, we should call that an experimental verifi- 

 cation. And, if still opposed, you go further, and say, 



