The first three perspectives of the philosophy of mind are those of dualism. These are Cartesian dualism, substance dualism and property dualism. Cartesian dualism is the idea that “mind and body are completely independent of each other and interact causally” (Vaughn 198). The major flaw of Cartesian dualism is that it is incompatible with science (Vaughn 206). This violates the causal closure of the physical, which asserts 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 major flaw of substance dualism is that it conflicts with the fundamental law of conservation. Property dualism is the idea that “mental properties are non-physical properties arising from, but not reducible to, physical properties” (Vaughn 224). Essentially, the major flaw of property dualism is similar to substance dualism, that is, there is no way to create non-physical properties that interact with physical properties (Vaugh 220). These three perspectives fit best with the epistemological view of skepticism, that is, “the view that we lack knowledge in some fundamental way” (Vaughn 317). Indeed, all three perspectives of dualism view the mental and the physical as distinct, and skepticism explains the lack of knowledge in certain areas, such as the mental in all three. Materialism is the “doctrine that every object and event in the world is physical” (Vaughan 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 with behaviorism is that it believes that mental states have nothing to do with our feelings, in fact mental states have a feeling. Moreover, it conflicts with our common-sense intuition that mental states often cause behavior (Vaughn 199). Identity theory is the view that “mental states are identical to physical states of the brain” (Vaughn 199). The main idea is that mental states are nothing more than brain states, in other words, the mind is the brain (Vaughn 199). The major flaw in identity theory is that if it is true, then knowing a person's brain states would allow one to know their mental states, but it is impossible to explain mental states with brain states (Vaughn 200 ). The other flaw is the idea that a mind could exist in an alien without it having a brain, then there is no link between mental states and brain states because there is no of brain. (Vaughan 200). Behaviorism and identity theory articulate with the epistemological view of rationalism, according to which "through unaided reason we can know what the world is like ».,”