Mechanistic materialism
Explanation
In opposition to Cartesian dualism, other thinkers of the seventeenth and eighteenth centuries took the opposite path: if everything in nature obeys mechanical laws, why should the mind be an exception? Thomas Hobbes stated it bluntly in Leviathan (1651): thinking is just the motion of internal particles. Consciousness would be nothing more than a particular kind of mechanism in operation.
This line found its most extreme expression in Julien Offray de La Mettrie, whose book Man a Machine (1747) maintained that the human body is a complex automaton and that all mental phenomena —desires, thoughts, emotions— are consequences of its physical workings. If animals are machines (as Descartes accepted), there is no reason humans should not be too: they are merely more sophisticated machines.
Mechanistic materialism is a monist position (there is only one substance, matter) and a reductionist one (all phenomena are explained by their parts and their physical interactions). In its classical version it conceived the universe as a great deterministic mechanism: given the initial state and the laws, the entire future would be fixed, including every human thought.
Its supporting arguments are strong: there is an enormous correlation between brain states and mental states, brain damage predictably alters the mind, drugs modify subjective states, and biological evolution explains in continuous fashion the appearance of minds out of mindless organisms. Ontological parsimony speaks in its favour: a single substance explains more with less.
Its weaknesses are also notable: the classical mechanics of the eighteenth century looks naive next to the quantum mechanics of the twentieth; strict determinism clashes with phenomenal freedom; above all, it does not explain why physical processes are accompanied by subjective experience. Even if we explain what the brain does, the question remains why there is something it is like to be that brain.
Contemporary materialism is much more nuanced: non-reductive physicalism, functionalism, biological naturalism and Russellian monism are heirs to that founding intuition but abandon the simplistic mechanical metaphor. Even so, La Mettrie's basic wager remains the majority view among professional philosophers: the mind, whatever it is, is something organised matter does.
Strengths
- Ontological parsimony: a single substance.
- Immediate compatibility with the development of the natural sciences.
- Eliminates the Cartesian interaction problem.
- Foundations for a naturalised psychology and anthropology.
Main critiques
- An overly simple reduction: it does not explain the subjective quality of experience.
- Low-level mechanism has been superseded by modern physics itself.
- Difficulty in accounting for intentionality and semantic content.
- The zombie argument and the hard problem reopen the question that mechanism thought it had closed.