In his early work Physical Causes of Truth (1775), he explained the connections between bodily perception, the brain, and the mind and the implications for philosophy.
He continued this line of inquiry with a two-volume work on neurophysiologically based logic entitled the Instruction of Sound Reason (1777).
In his Something about Kantian Philosophy in relation to the Proof of the Existence of God (1789), he argued against Immanuel Kant that simple conclusions should be sufficient for philosophical justification.
He also argued for defining philosophical terms and concepts through descriptions of physical and neurophysiological changes in the organs and in the context of concrete examples.
In opposition to what he considered to be the overly abstract and metaphysical approaches of Christian Wolff and Kant, his four-volume work New General Philosophical Analytical Lexicon appeared in 1803.