154 THE SCIENCE OF LOGIC 



(d] Rocks exposed to glacial action are seen to become 

 scored or striated. 



Many rocks in this particular district are thus scored or 

 striated. 



Therefore, this district has probably been the scene of glacial 

 action. 



(e) In districts now exposed to glacial action we find perched 

 boulders. 



In this district we also find perched boulders. 



Therefore, etc. as in (d}. 



(/) In districts now exposed to glacial action we find long 

 lines of accumulated stones and debris, which are called 

 &quot; moraines &quot;. 



In this district we find such &quot; moraines&quot;. 



Therefore, etc. as in (d). 



From those examples we see that the argument from analogy 

 naturally assumes the form of a syllogism in the second figure 

 with two affirmative premisses ; that, therefore, it does not/rav 

 the law suggested in the conclusion, but only makes the con 

 clusion more or \zss probable ; that this probability may, perhaps, 

 be a practically worthless and groundless suspicion ; or that it 

 may amount to moral certitude : especially when, as in (d}, (e\ 

 and (/), we have a number of independent analogical inferences 

 all pointing to the same conclusion. 



The formal reason why we cannot derive a universal law 

 with certitude as conclusion from the premisses of such an argu 

 ment, is that it would involve the fallacy of undistributed middle. 

 Until we can convert our major premiss simply [from &quot; All P is 

 M&quot; to &quot; All M is P&quot;], and so construct a syllogism in the first 

 figure, we cannot be sure of our conclusion. We are not sure 

 in () that the symptoms in which the particular disease agrees 

 with cholera can be due only to the action of a bacillus ; or in (b) 

 that the points in which Mars resembles the earth are sufficient 

 and indispensable for organic life ; or in (c] that the ground for A s 

 action is x, in which he agrees with B, rather than R, in which 

 he differs from B ;^ or in (d), (e), (/), that the scorings, perched 

 boulders, and &quot; moraines &quot; in question, might not possibly be ac 

 counted for otherwise than by glacial action. And the only way 

 we can become sure of these things (and so convert our major 

 premiss and prove our conclusion) is by a closer investigation of 

 1 C/. WELTON, op. cit., ii., pp. 71-3. 



