INDUCTION IN ITS VARIOUS SENSES 53 



&quot; There is an enormous number of general propositions, which we accept 

 for no better reason than that the facts are inconsistent with our denying them, 

 and not because in themselves they have anything which could have led us to 

 suppose them true, antecedently to our experience. When it is said that we 

 ought always to follow experience, it is meant that we ought not to trust our 

 notions of what seems antecedently fit to be true, or mere guesses as to the 

 connexions that subsist in nature, but accept only those connexions which our 

 experience forces us to accept because it is inconsistent with any alternative. 

 Such reasoning is called a posteriori, because it starts from the facts, which 

 are conceived as logically dependent on, or posterior to, their principles, and 

 thence infers the principles on which they are dependent. Conversely, 

 deductive reasoning is often called a priori, because it starts from the 

 principles or conditions, which are conceived as logically prior to the con 

 sequences that follow from them l . . . . But it is an error to suppose that all 

 general principles are arrived at a posteriori or by process of merely showing 

 that facts are not consistent with any other. . . . Still it is true that in the 

 inductive sciences the vast majority of our generalizations are reached either 

 in this a posteriori manner, or by the help of deductions from other general 

 izations so reached. And it may be well to show by one or two examples how 

 generalizations that rest merely on induction present as it were a blank wall 

 to our intelligence, as something at which we cannot help arriving, but which 

 we can in no way see through or make intrinsically plausible.&quot; 2 The author 

 goes on to cite examples &quot; to illustrate . . . what Bacon would call the 

 surd and positive character of conclusions resting only on induction &quot;. 3 One 

 of these examples will be sufficient here : &quot; Facts show that the excision of 

 the thyroid gland dulls the intelligence : could any one see that this must be 

 so ? Explanation may show that on a contribution which the gland, when 

 properly functioning, makes to the circulating blood depends the health of the 

 brain ; but that comes later than the discovery of the effects of excision ; and 

 even so can we understand the connexion, which facts establish, between 1 the 

 state of the mind and the health of the brain ? &quot; 4 



These extracts will show a clear and intelligible distinction between two 

 ideals of the knowledge we aim at by inference : the knowledge that ceitain 

 things are so, and the further knowledge why they are so ; and, by way of 

 consequence, between &quot; inductive &quot; forms of inference, which naturally sub 

 serve the former ideal, and &quot; deductive,&quot; &quot; demonstrative,&quot; &quot; explanatory &quot; 

 forms of inference, which subserve the latter ideal. Some of these points will 

 receive further notice later, in the chapter on Explanation. 



213. RELATION OF ANTECEDENT TO CONSEQUENT IN DE 

 DUCTION AND INDUCTION : THE LATTER CONSIDERED AS AN 

 &quot; INVERSE PROCESS &quot;. We have seen that the logical inferences 

 involved in the inductive process assume one or other of the forms 

 commonly recognized in &quot; formal &quot; or &quot; deductive &quot; logic ; and that 



1 &quot; Or, in another sense, illustrated inmost mathematical reasoning, because the 

 premisses, without being more general than the conclusion, or giving the cause 

 why it is true, are not based upon an appeal to facts which might conceivably have 

 been otherwise.&quot; 



3 JOSEPH, op. cit. t pp. 400, 401. 3 6&amp;lt;f., p. 402. *ibid., p. 401. 



