MindThe philosophy of the mind deals with the examination of a family of problems revolving around the concept of the mind. The mental may be distinguished from the physical in various ways: intentionality and consciousness provide two important features of mental states. One extreme position in the philosophy of mind is represented by Descartes' dualism, where it is claimed that minds are utterly distinct substances. An important part of Descartes' argument for this position is the claim that mental states are known in a special way: they are directly given, transparent to their owner and known infallibly. This position has been sharply attacked by Wittgenstein, who argued (in his private language argument) that Descartes' view makes knowledge of other people's minds impossible, and that our understanding of the mind is bound up with behaviour. Philosophers of a monist and materialist bent, who believe that reality is physical and explained by natural science, have sought in various ways to understand the mind in material terms. Behaviourism, now unfashionable, advocated that psychology should concern itself exclusively with observation of behaviour, disregarding introspection altogether. Others have proposed bluntly that mental states are the same as states of the brain. Dissatisfaction with these overly simple attempts to incorporate the mental into the physical realm led to the development of functionalism. This view grew out of attention to the analogy between minds and computers, and has itself been subject to criticism arising out of development in the theory of artificial intelligence.DualismDualism is the general philosophical claim that the world is composed of two ultimate different kinds of substance, typically mind and matter. Monism, by contrast, holds that the world is composed of but one kind of substance. Descartes is usually credited with having provided the most significant articulation of dualism, according to which the world is composed of a single material substance (nature), which is extended and divisible, and a plurality of mental or immaterial substances (God and the minds of individual persons), each of which is un-extended and indivisible. Dualism in all of its forms leads to the notorious problem of interaction: namely, of understanding how substances of different kinds can affect one another. Descartes sought to resolve this problem in the case of human beings by claiming that a particular part of the brain (the pineal gland) is responsible for co-ordinating the relations of mind and body. Descartes' solution depends, however, upon the role of God in instituting this arrangement, and a frequent objection to modern, secular dualists is that they have no alternative way of explaining the relation of mind and body. In theology, dualism refers to the perception of the world as motivated by opposing principles of good and evil, as in, for example, Parsi and some Christian sects' beliefs.MonismMonism is the philosophical belief that the world consists entirely of a single substance or kind of substance. Opposed to the dualism of mind and body, the most obvious forms of monism claim either that the world is entirely material (materialism) or that it is entirely mental (idealism). Monist doctrines will frequently explain the apparent differences between kinds of things as subjective, resulting from our different ways of understanding a single thing. The most extreme monism, held, for example, by Spinoza, claims that the world is a single thing, and that all seeming diversity is a product of partial understanding.NousNous, in conversational use, it means reason as distinct from sense. In philosophy, nous is considered to be the faculty of intellectual apprehension and of intuitive thought.