This book deals with the Psychology of Genius and the relation between Genius and Insanity.

"The psychological analysis of famous poets will show that the intellectual function is no whit less important a factor of poetic genius than fancy itself, although the latter is the one immediately employed in the act of composition. We have seen that creative fancy works with the material which former impressions of sense have left behind as their remains or residua. The more comprehensive the knowledge of the poet, therefore, and the more he is in condition to assimilate and compact the impressions the world conveys to him, and the sounder and truer his judgments of persons and situations, and the more methodical his thought and the better his memory, by so much the more will his fancy display luxuriance, and so much more various will be his creations.