The objections to the mind/body theory: numerical identities are necessary truths, aliens (has mental states but no brain) and zombies (look like a human and has brain but doesn"t have mental states) both seem to be possible. Responses: conceivability doesn"t entail possibility, expand: human brain is identical to the mind, a mind = alien brain. Clark kent = superman - its possible that clark kent was never superman: the names both refer to the same guy. Identity definition- the mind is defined as a mind and vice versa: ex. pain is identical to parts of the brain, functional definition, ex. The definition of a president- define them in terms of what it is that they do. Two claims: mental states are functions in a causal network. Caused different stress, injury, etc. by many things- I belief have a headache) can be a desire (ex. The belief will cause you to say i have a headache.