54 SCIENTIFIC METHOD IN PHILOSOPHY 



empirical. But between the two lies a vast intermediate 

 region, which we must now briefly explore. 



" Molecular " propositions are such as contain conjunc- 

 tions if or, and, unless, etc. and such words are the marks 

 of a molecular proposition. Consider such an assertion 

 as, " If it rains, I shall bring my umbrella.' , This 

 assertion is just as capable of truth or falsehood as the 

 assertion of an atomic proposition, but it is obvious that 

 either the corresponding fact, or the nature of the cor- 

 respondence with fact, must be quite different from what 

 it is in the case of an atomic proposition. Whether it 

 rains, and whether I bring my umbrella, are each severally 

 matters of atomic fact, ascertainable by observation. But 

 the connection of the two involved in saying that if the 

 one happens, then the other will happen, is something 

 radically different from either of the two separately. 

 It does not require for its truth that it should actually 

 rain, or that I should actually bring my umbrella ; even 

 if the weather is cloudless, it may still be true that I 

 should have brought my umbrella if the weather had 

 been different. Thus we have here a connection of two 

 propositions, which does not depend upon whether they 

 are to be asserted or denied, but only upon the second 

 being inferable from the first. Such propositions, there- 

 fore, have a form which is different from that of any 

 atomic proposition. 



Such propositions are important to logic, because all 

 inference depends upon them. If I have told you that 

 if it rains I shall bring my umbrella, and if you see that 

 there is a steady downpour, you can infer that I shall 

 bring my umbrella. There can be no inference except 

 where propositions are connected in some such way, so 

 that from the truth or falsehood of the one something 

 follows as to the truth or falsehood of the other. It 



