This early work by Malcolm Guthrie was originally published in 1882 and we are now republishing it. 'On Mr. Spencer's Unification of Knowledge' is a critique of the general logical construction of Spencer's philosophy. Herbert Spencer was born on 27th April 1820, in Derby, England. In 1851 he published 'Social Statics' to great acclaim and his quietly influential 'Principles of Psychology' in 1955. These were followed by numerous works of sociology, psychology, and philosophy, which led him to become a prominent intellectual of his day. He also wrote 'The Developmental Hypothesis' (1852) which described the theory of evolution seven years before Charles Darwin's 'Origin of Species'. He even popularised the term "Evolution" and coined the phrase "Survival of the fittest," but his works did not contain the comprehensive theoretical system that Darwin's did, which is why his theory was not taken seriously at the time. Spencer's most famous idea was that of "Social Darwinism." He saw the process of organic evolution as being analogous to that of society, an idea influenced many intellectuals of the day.