On materialism/physicalism, all mental phenomena are identical with material interactions and as such are entirely governed by the laws of physics. Predictability, it's what allows science to exist as a discipline.
Under that view, the thought you are having at this moment can be no different given the arrangement of all of the particles in the universe immediately preceding that "thought".
So, why do materialists argue with anyone? Why is the thought of arguing with a tree that it shouldn't have grown a leaf irrational? Why is the thought of arguing with a supercomputer that it shouldn't have come to the conclusion it did irrational, but arguing with a person that it shouldn't have come to the conclusion they did rational?
Can it ever be rational to argue with any entity that is doing the only thing it can do given the current arrangement of particles in the universe?
Materialism is a form of philosophical monism which holds that matter is the fundamental substance in nature, and that all phenomena, including mental phenomena and consciousness, are identical with material interactions.
Materialism is closely related to physicalism, the view that all that exists is ultimately physical. Philosophical physicalism has evolved from materialism with the discoveries of the physical sciences to incorporate more sophisticated notions of physicality than mere ordinary matter, such as: spacetime, physical energies and forces, dark matter, and so on. Thus the term "physicalism" is preferred over "materialism" by some, while others use the terms as if they are synonymous.
