Matter and Memory is a book of cognitive philosophy by Henri Bergson which discusses the classic problem of how the human mind and its memories are related to the spirit. Bergson uses the phenomena of memory to construct arguments in favor of the spirit's existence. The various types of memory, and how they are related to the physical world, are discussed. Bergson analyses how memories are formed, what bearing they have on the world, and how they ultimately come to constitute their possessor's innate spirit. This book was originally written by Bergson in response to an essay by Theodule Ribot, who held that all memory could be traced back to the brain's nervous system. Thus, the essence of human memory could be reduced to mere matter, rather than containing a higher, spiritual element. Bergson fervently disagreed with this opinion, and strove to write this thesis as a counter to the notion that the spirit can be reduced to only molecular activity.