George Boole 
Mathematical Analysis of Logic [PDF ebook] 
Being an Essay Towards a Calculus of Deductive Reasoning

Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. That which renders Logic possible, is the existence in our minds of general notions, – our ability to conceive of a class, and to designate its individual members by a common name.