232 THE SCIENCE OF LOGIC 



real order, appears to be too narrow and one-sided ; nor does he show clearly 

 how it is to be connected with our inductive and a posteriori reasoning from the 

 facts of experience, so as to help us in building up a synthetic world-view, or 

 philosophy of the universe as a whole. He was right in holding that our 

 scientific knowledge of any individual fact could never surpass what is deducible 

 from the specific type embodied in it, or reach to the individual, accidental, 

 determinations of the fact ((rv/xj37Kora). But he is not clear as to how we 

 reach the necessary and universal judgments which give us knowledge about 

 real essences, outside the domain of the purely abstract sciences. If he de 

 manded for them the &quot; ipse dixit of an incommunicable intuition &quot; * he demanded 

 what people generally will say is not forthcoming. He does seem to have held 

 that such principles are not reached by any process of inductive generalization, 

 or a posteriori reasoning from experience. And yet, outside the limited domain 

 of abstract mathematics and metaphysics, where we have self-evident intuitions 

 of possible essences, the only means we have of discovering and establishing 

 scientific truths, i.e. necessary and universal truths, about the actual world, are 

 induction and a posteriori reasoning. 



254. PRINCIPAL KINDS OF PROOF. (a) Causal or &quot; A priori&quot; 

 Proof; Proof of Fact or &quot; A posteriori&quot; Proof ; &quot;A Simultaneo&quot; 

 Proof. Besides strict Causal Demonstration, by which we know 

 anything scientifically through a knowledge of all its causes, and 

 of the way in which it is produced by its causes (aTroSe^t? BIOTI : 

 demonstratio propter quid : proof which shows the causes of any 

 thing), 2 there is a sort of demonstration called Proof of Fact. 

 (a7ro8eti? art or el ecrri : demonstratio quia), which gives us certi 

 tude that a thing is so, without explaining to us why it is so. 

 It falls naturally into a syllogism in the first figure, and differs 

 from the demonstrative syllogism proper only in this, that it has 

 for middle term not a &quot;cause&quot; which is prior to the conclusion 

 in the real order, fyvcrei, or \6yy -rrporepov but some &quot; effect &quot; 

 or otherwise connected fact which, though not really prior to the 

 conclusion, is prior to it in our experience (yfiiv Trporepov), and 

 is for us a sure evidence (rex^piov 3 ) of the truth of the conclu 

 sion. Thus, when we argue from an effect that the supposed 

 cause is such or such, our argument will be cogent if we know 

 that no other cause could account for the effect in question. This 

 is often possible, as, for instance, in the diagnosis of a disease by 

 studying the patient s symptoms. So, also, when, in virtue of the 

 principle of causality, we argue from the existence of an effect to 

 the existence of an adequate cause, we are making valid use of 



1 JOSEPH, op. cit., p. 357. 



2 Cf. Anal. Post., ii. f cap. x. [xi.], i, where Aristotle enumerates the four causes. 



3 Rhet., i., c. ii., 16, 17. Aristotle mentions this proof in connexion with the 

 Enthyweme. Cf. JOSEPH, op. cit., p. 323 n. ; supra, 234-5. 



