That the mind is a purely physical substance.

1) The Argument from Causal ClosureAxiom - Every caused event has a physical cause.P1 - Mental events cause physical events.By observing our behaviours in the physical world, we see that this premise appears to be true. A mental event such as an emotion, thought or desire clearly leads people to act upon these mental events. The classic example of this is that my mental desire to lift my arm causes me to physically lift my arm. One might object to this premise and adopt a position known as epiphenomalism. This however appears rather troubling, if for instance someone whom I am talking to is claiming to be experiencing the mental event of a pain or of a pleasure, it seems that I do not have any reason to believe this to be so, given that said person's pleasure or pain is not the cause of their claim. Evolutionarily speaking, it seems absurd that we would evolve mental at all, if they are not the cause of our physical events which lead our survival and reproduction. This also leads to significant problems regarding the existence of other minds - the main reason that we believe a person to be in pain while bleeding or crying is because we are in pain when bleeding or crying, but this does not seem reasonable unless we are to suppose that these physical events are caused by the mental event of pain - epiphenomalism denies this.P2 - That mental events supervene upon physical eventsCommonly formulated as "If an event e causes event e*, then there is no event e# such that e# is non-supervenient on e and e# causes e*."[1], the exclusion principle is perhaps better illustrated by example. Take for instance the previous example that if I desire to lift to my arm, and this causes me to lift my arm, then there are no events that is non-supervenient (ie. dependant upon) to the desire to lift my arm that also causes me to lift my arm. One might try to object to the exclusion principle by claiming that something can be overdependant, for instance, if more than one gunman shoots down the same person, then it would appear that in this case the exclusion principle is false. What this fails to do is provide an explanation of how such exceptions could be so widespread. Surely we are not claim that every single mental-pysical interaction throughout the history of such interaction has been an instance of overdependance.C Physicalism is trueThis follows, given it has been shown that mental events supervene on the physical.2) The Argument from Methodological NaturalismAxiom - It is rational to base our metaphysical beliefs upon the methods of natural science.P1 - The methods of science lead to a physicalist metaphysical system.That this is true should be obvious. Science has, time and time again, given naturalistic and non-teleological explanations for previously inexplicable phenomena. Take for instance the intricate design of the snowflake, or the astonishing and time-tested order of the beautiful rainbow - all of these were once regarded as proofs that their origin must be non-naturalistic, and the product of divine order. Science however cannot make this assumption, it bases itself upon the fundamental idea that we must try to come up with physicalist explanations that are in accordance with the laws of nature. Given the huge body of evidence for the physical, and the highly contentious body of evidence for the non-physical, we must therefore, as per Occam's razor, go for the physicalist explanation, as this is most strongly in accordance with our other experiences and observations.C It is rational to be a physicalistThis follows from the first two premises.References1 - http://plato.stanford.edu...