"Man a Machine" by Julien Offray de La Mettrie is a work of materialist philosophy first published in 1747. Extending Descartes' view of animals as automatons, La Mettrie argues that humans are also machines. He rejects the existence of a soul separate from matter, demonstrating how physical conditions—sleep, nutrition, drugs—directly affect what we call the mind. This controversial work denies dualism and proposes that body and soul are inseparably one.
Wikipedia page about this book: en.wikipedia.org/wiki/Man_a_Machine