Rejecting the Premise of Interactionalism: Parallelism, Epiphenomenalism and – surprisingly – Eliminative Materialism

Rejecting the idea that mental phenomena can cause physical phenomena, makes it possible to accept both other premises:

Mental phenomena are not identical to physical phenomena.

Every physical phenomenon has a physical cause.

Let’s have a look at some Philosophy of Mind theories that would be compatible with this choice:

Psychophysical Parallelism

Psychophysical Parallelism can be traced back to Leibniz and Geulincx, and is acting on the assumption that the physical and the mental sphere are completely independent. These postulate causal effects within the mental sphere, as well as within the physical one, but no causal effects between them. Every correlation between these two areas is just accidental, not nomological. They two chain of events are just somehow aligned – in a kind of predispositioned harmony that might lead to certain mental states always occuring together with certain physical states. Well, especially in times where preharmonizing creators are not so fashionable, this is a rather unpopular theory.


Epiphenomenalism is overcoming this problem with claiming that even though physical states might cause mental ones, mental states do not have any causal effects, neither on following mental states nor on physical states. This position traces back to Thomas Henry Huxley, who rejects Descartes’ view, that animals are unconscious automata. He tried to reconcile his naturalist view on nature with his strong intuition, that mental states are different from physical ones, by downgrading mental states to pure epiphenomena. In a way, you might see mental states simply as the way how it feels for a complex biological system to be in a certain physical state.

Eliminative Materialism

Followers of this theory are maintaining that mental states simply do not exist at all. To illustrate this argument eliminative materialists are comparing today’s situation with earlier ones. Like in the 18th century it turned out, that phlogiston does not exist, it will be turning out in the future, that mental states – states on which terms of the so called folk psychology refer to – do not exist. Eliminative materialism is ontologically different from the identity theories, as the former is claiming identity between mental and physical states, while the latter simply puts no trust in the existence of mental states. According to linguistics they also differ, as eliminative materialists
from their conception draw the conclusion that it won’t make sense to keep alive terms referring to mental states.

This fact caused me to impute eliminative materialism as being forced to act on the Bieri-Trilemma in accepting sentences #1 and #3 and rejecting #2. In stating that only physical things exist and in stating that the mental does not exist at all, the thesis that mental states are identical physical states is in my eyes unsustainable for eliminative materialists. So, although epiphenomenalism and eliminative materialism act in the same way on
the Bieri-Trilemma like psychophysical parallelism does, they come to another conclusion about the efficacy of mental states. While psychophysical parallelism concedes mental states to at least have effects on following mental states, epiphenomenalism and eliminative materialism – as different as these theories may otherwise be – agree in postulating no causal efficacy for mental states.