AN INVESTIGATION 



OF 



THE LAWS OF THOUGHT 



CHAPTER I. 



NATURE AND DESIGN OF THIS WORK. 



1. '"pHE design of the following treatise is to investigate the 

 r*- fundamental laws of those operations of the mind by which 

 reasoning is performed; to give expression to them in the symboli- 

 cal language of a Calculus, and upon this foundation to establish the 

 science of Logic and construct its method ; to make that method 

 itself the basis of a general method for the application of the ma- 

 thematical doctrine of Probabilities ; and, finally, to collect from 

 the various elements of truth brought to view in the course of 

 these inquiries some probable intimations concerning the nature 

 and constitution of the human mind. 



2. That this design is not altogether a novel one it is almost 

 needless to remark, and it is well known that to its two main 

 practical divisions of Logic and Probabilities a very considerable 

 share of the attention of philosophers has been directed. In its 

 ancient and scholastic form, indeed, the subject of Logic stands 

 almost exclusively associated with the great name of Aristotle. 

 As it was presented to ancient Greece in the partly technical, 

 partly metaphysical disquisitions of the Organon, such, with 

 scarcely any essential change, it has continued to the present 

 day. The stream of original inquiry has rather been directed 

 towards questions of general philosophy, which, though they 



