Who was one of the first modern philosophers to propose a purely materialist monist approach to the mind-body problem?

The focus on materialist monism in the context of the mind-body problem is closely associated with Julien de La Mettrie. He is recognized for his work "L'Homme Machine" (Man a Machine), in which he argued that humans are essentially complex machines, and consciousness and thought processes are entirely products of physical processes in the body. This perspective represents a significant shift towards a materialist outlook where mental states are seen as entirely dependent on physical states, thus denying any spiritual or non-physical substance in understanding human experience.

Although Pierre Gassendi was an early advocate for a version of materialism, his views were more nuanced and were influenced by both empirical observations and Cartesian dualism. His discussions were not as strictly materialist as La Mettrie's, which places La Mettrie firmly as one of the pivotal figures in proposing a purely materialist worldview concerning the mind-body relationship. This foundational idea set the stage for later developments in psychology and philosophy regarding the nature of consciousness and the relationship between mental and physical states.