OF ARTS AND SCIENCES : MAY 14, 1867. 287 



Induction may, therefore, be defined as argument which assumes 

 that a whole collection, from which a number of instances have been 

 taken at random, has all the common characters of those instances ; 

 hypothesis, as an argument which assumes that a term which necessa- 

 rily involves a certain number of characters, which have been lighted 

 upon as they occurred, and have not been picked out, may be predi- 

 cated of any object which has all these characters. 



There is a resemblance between the transposition of propositions by 

 which the forms of probable inference are derived and the contraposi- 

 tion by which the indirect figures are derived ; in the latter case there 

 is a denial or change of modal quality ; while in the former there is 

 reduction from certainty to probability, and from the sum of all re- 

 sults to some only, or a change in modal quantity. Thus probable 

 inference is related to apagogical proof, somewhat as the third figure 

 is to the second. Among probable inferences, it is obvious that 

 hypothesis corresponds to the second figure, induction to the third, 

 and analogy to the second-third. 



Five hundred and eighty-second Meeting. 



May 14, 1867. — Monthly Meeting. 



The President in the chair. 



The Corresponding Secretary read letters relative to ex- 

 changes. 



The President read a letter from Dr. J. Mason Warren, pre- 

 senting to the Academy a copy of his work on " Surgical 

 Operations." 



The following paper was presented : — 



On a New List of Categories. By C. S. Peirce. 



§ 1. This paper is based upon the theory already established, that 

 the function of conceptions is to reduce the manifold of sensuous im- 

 pressions to unity, and that the validity of a conception consists in the 

 impossibility of reducing the content of consciousness to unity without 

 the introduction of it. 



§ 2. This theory gives rise to a conception of gradation among those 

 conceptions which are universal. For one such conception may unite the 

 manifold of sense and yet another may be required to unite the con- 

 ception and the manifold to which it is applied ; and so on. 



