ILLUSTRATIONS OF THE LOGIC OF SCIENCE. 473 



not explain what we have seen, namely, all these documents and monu- 

 ments, without supposing that he really existed. Hypothesis again. 



As a general rule, hypothesis is a weak kind of argument. It often 

 inclines our judgment so slightly toward its conclusion that we cannot 

 say that we believe the latter to be true ; we only surmise that it may 

 be so. But there is no difference except one of degree between such 

 an inference and that by which we are led to believe that we remember 

 the occurrences of yesterday from our feeling as if we did so. 



II. 



Besides the way just pointed out of inverting a deductive syllogism 

 to produce an induction or hypothesis, there is another. If from the 

 truth of a certain premise the truth of a certain conclusion would neces- 

 sarily follow, then from the falsity of the conclusion the falsity of the 

 premise would follow. Thus, take the following syllogism in Barbara: 



Mule. All men are mortal. 

 Case. Enoch and Elijah were men. 

 .*. Result. Enoch and Elijah were mortal. 



Now, a person who denies this result may admit the rule, and, in 

 that case, he must denv the case. Thus : 



Denial of Result. Enoch and Elijah were not mortal. 

 Rule. All men are mortal. 

 .. Denial of Case. Enoch and Elijah were not men. 



This kind of syllogism is called Baroco, which is the typical mood 

 of the second figure. On the other hand, the person who denies the 

 result may admit the case, and in that case he must deny the rule. 

 Thus : 



Denial of the Result. Enoch and Elijah were not mortal. 

 Case. Enoch and Elijah were men. 

 .. Denial of the Rule. Some men are not mortal. 



This kind of syllogism is called Bocardo, which is the typical mood 

 of the third figure. 



JBaroco and Bocardo are, of course, deductive syllogisms ; but of a 

 very peculiar kind. They are called by logicians indirect moods, be- 

 cause they need some transformation to appear as the application of a 

 rule to a particular case. But if, instead of setting out as we have here 

 done with a necessary deduction in Barbara, we take a probable deduc- 

 tion of similar form, the indirect moods which we shall obtain will be 



Corresponding to Baroco, an hypothesis ; 

 and, Corresponding to Bocardo, an induction. 



For example, let us begin with this probable deduction in Barbara : 



