Trialism in philosophy was introduced by John Cottingham as an alternative interpretation of the mind–body dualism of Rene Descartes. Trialism keeps the two substances of mind and body, but introduces a third substance, sensation, belonging to the union of mind and body. This allows animals, which do not think like humans, to be regarded as having sensations and not as being mere automata.
Although composed of two substances, mind and body, the human being possesses distinctive attributes in its own right (including sensations, passions, emotions), and these form a third category, that cannot be reduced to thought or extension.[3] Cottingham has also argued that Descartes’s view of animals as ‘machines’ does not have the reductionistic implications commonly supposed.[4] Finally, Cottingham has explored the importance of Descartes as a moral philosopher, with a comprehensive picture of the good life that draws both on his scientific work (in physiology and psychology) and also on the theistic outlook that informs all his philosophy.[5] Cottingham is co-editor and translator of the three-volume Cambridge edition of The Philosophical Writings of Descartes.[6]
Kong Derick has also introduce the term Derician Trialism, in which he maintains the two substances of mind and body of Descartes and substituted the sensation substance of Cottingham due to it limitations, with the substance he calls Submind, which involves the processes of memories, sensations, emotions and reflexes. He also says that animals do have a submind which makes them to be subconscious.