This book presents an English synopsis of five of the most influential works written in the early twentieth century (in Spanish originally) by the Argentinian philosopher and psychiatrist Jose Ingenieros (1877-1925). They are presented together in English translation in one book for the first time. The Introductory Chapter is a biographical note on Ingenieros, who was Professor of Experimental Psychology at the Faculty of Philosophy and Letters of the University of Buenos Aires. The topics covered include biological psychology, criminology, ethics, and philosophy."