166 MEMOIR OF AUGUSTUS DE MORGAN. 



1 847. science,' says his biographer, c then became his study, 

 Dr. Boole. Mathematics his recreation; yet it is a remarkable fact 

 that his more important and valuable Mathematical works 

 were produced after he had commenced his Psychological 

 investigations.' ! In 1847, his attention having been 

 drawn to the subject by the publication of Mr. De 

 Morgan's Formal Logic, he published the Mathematical 

 Analysis of Logic, and in the following year communicated 

 to the Cambridge and Dublin MathematicalJournal a paper 

 on the Calculus of Logic. His great work, An Investigation 

 into the Laws of Thought, on which are founded the Mathe- 

 matical Theories of Logic and Probabilities, was a develop- 

 ment of the principle laid down in the Calculus, its design 

 being ( to investigate the fundamental laws of those opera- 

 tions of the mind by which reasoning is performed ; to 

 give expression to them in the symbolical 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 Mathematical doctrine of probabilities ; and, finally, 

 to collect from the various elements of truth, brought to 

 view in the course of these inquiries, some probable inti- 

 mations concerning the nature and constitution of the 

 human mind.' 



I have given Dr. Boole's own statement of the design 

 of his work at length because it conveys in few words, not 

 only some idea of the aim of his investigations, but of the 

 relations between the three sciences of Psychology, Mathe- 

 matics, and Logic. An estimate of his mental work and 

 its value to science was given in a few words, after his 

 death in 1864, by my husband : 



6 His first paper in the Cambridge Mathematical 

 Journal contains remarkable speculations which can here 

 be described only in general terms, as extensions of the 

 power of algebraic language. These papers helped to 



1 Taken substantially from a notice of Dr. Boole in the Obituary 

 Notices of the Royal Society, by the Rev. R. Harley. 



