The first three perspectives of the philosophy of mind concern dualism. They are Cartesian dualism, substance dualism, and property dualism. Cartesian dualism is the view “That mind and body are completely independent of each other and interact causally” (Vaughn 198). The main flaw of Cartesian dualism is that it is incompatible with science (Vaughn 206). It violates the causal closure of the physical, which states a physical cause for every physical effect and that non-physical or mental causes are excessive (Vaughn 206-207). Substance dualism is the idea “That the mind and body are made up of two fundamentally different kinds of things, or substances,” (Vaughn 198). The main flaw of substance dualism is that it conflicts with the fundamental law of conservation. Property dualism is the view “That mental properties are nonphysical properties arising from, but not reducible to, physical properties” (Vaughn 224). Essentially, the main flaw of property dualism is similar to substance dualism, that is, there is no way to create nonphysical properties that interact with physical properties (Vaugh 220). All three of these perspectives fit best with the epistemological view of skepticism, or “The idea that we lack knowledge in some fundamental way” (Vaughn 317). This is because the three perspectives of dualism see the mental and the physical as distinct, and skepticism explains the lack of knowledge in some areas, such as the mental in the three. Materialism is the “Doctrine that every object and event in the world is physical” (Vaughn 198). Materialism has many theories of mind, two of which are logical behaviorism and identity theory. Logical behaviorism is “the idea that mental states are dispositions to behave in particular ways under certain circumstances” (Vaughn 199). A flaw of behaviorism is that it believes that mental states have nothing to do with our feelings, in fact mental states feel something about them. Furthermore, it is at odds with our commonsense intuition that mental states often cause behaviors (Vaughn 199). Identity theory is the view “That mental states are identical to physical states of the brain” (Vaughn 199). The main claim is that mental states are nothing more than brain states, in other words, the mind is the brain (Vaughn 199). The main flaw of the identity theory is that, if it were true, then knowing a person's brain states would allow knowledge of their mental states, but it is impossible to explain mental states with brain states (Vaughn 200). The other flaw is the thought that a mind can exist in an alien without it having a brain, so there is no connection between mental states and brain states since there is no brain. (Vaughn 200). Both behaviorism and identity theory are intertwined with the epistemological vision of rationalism, that is, “Through reason alone we can come to know what the world is like,”