Minds and Computers : An Introduction to the Philosophy of Artificial Intelligence
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- Figure 4.5 Model synapse. synaptic cleft pre-synaptic terminal Axon post-synaptic structure synaptic vesicles
soma
dendrites myelin sheath synapse axon Figure 4.4 Model neuron. di fference in electrical potential between the inside of the cell and the outside of the cell rises. When this potential di fference is high enough, the soma will discharge an electrical impulse along its axon and return to its resting potential. This is something of a simplification but it su ffices for our purposes. If you’re feeling a little overwhelmed with all these technicalities and all this new terminology, don’t fret. All you really need to take away from this chapter with respect to the operations of neurons is the fol- lowing. There are very many neurons in the brain which are highly inter- connected. These neurons function by passing electrical signals to each other. If a neuron receives su fficient incoming signals from other neurons, it will send out a signal of its own. Those readers who are intrigued by what they’ve read here and would like to learn more are advised to follow the suggestions for further reading. 34 Figure 4.5 Model synapse. synaptic cleft pre-synaptic terminal Axon post-synaptic structure synaptic vesicles C H A P T E R 5 AUSTRALIAN MATERIALISM Now that we have at least a rudimentary understanding of just what an amazing thing the human brain is, it is time to examine a philoso- phical theory which posits a very strong connection between the neural and the mental. Australian materialism – so called as its major proponents were located in Australian universities – is a theory which goes by many names. It is variously also known as reductive materialism, identity theory, type physicalism and central state materialism, for reasons which will become apparent in due course. It will serve our purposes here to develop Australian materialism in conjunction with another theory: the causal theory of mind. When we ask the question ‘what are mental states?’, there are two distinct kinds of answer one can provide. One kind of answer involves giving a conceptual analysis of mental states – an account of what we mean by ‘mental states’. Another kind of answer involves providing a substantive identification – indicating which things turn out to be mental states. In the case of behaviourism, these two kinds of answer to the ques- tion of what mental states are were conflated in the one theory. This is because behaviourists are eliminativists about mental states and, hence, do not believe there is a substantive identification to be made. They hold that talk of mental states is, in fact, just talk about dispos- itions to behave – behaviourism is an ontologically eliminative and semantically reductive theory of mind. We’re now going to employ more philosophical sophistication and carefully tease apart the two ways of answering the question of what mental states are. Australian materialism will provide us with the sub- stantive identification – the account of which things turn out to be mental states. The account of what it is to be a mental state, however, will be provided by the causal theory of mind. 35 5.1 THE CAUSAL THEORY OF MIND The canonical exposition of the causal theory is given by David Armstrong in his 1968 monograph, A Materialist Theory of Mind. Armstrong, together with J. J. C. Smart and U. T. Place, is one of the three major figures associated with Australian materialism. The causal theory, as we have said, aims to give an account of what it is to be a mental state. This is, if you will, very much like providing a job description for mental states. A job description does not specify the race, age or gender of the occupant of the role. It merely tells us what the relevant duties are – what one has to do in order to fill the role. So it is with the causal theory – it tells us what something has to do in order to fill the role of a mental state. We begin by reflecting on the fact that many terms in our language are defined by reference to their causal powers. The term ‘poison’ is a paradigm example. A poison can be a liquid, a solid or a gas. Poisons can be coloured or colourless; they can be odourless or have a distinctive odour, and so on. None of these properties are relevant to whether or not the substance in question is properly called ‘poison’. What makes a substance a poison is its causal role with respect to bringing about ill health in humans. To cast this as a definition we can say the following: a substance is a poison i ff it is apt to cause ill health in humans. The central tenet of the causal theory is that mental state terms are just such terms. We define mental state terms, according to the causal theorist, by reference to their causal role with respect to behaviour. This allows the causal theorist to provide a schema for defining Download 1.05 Mb. Do'stlaringiz bilan baham: |
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