Mind: A Brief Introduction (John R. Searle) / quote 115 of 138
Demystifying intentionality through biology
We are speaking, as we did about consciousness, of a certain set of biological capacities of the mind. And it is best to start with the biological capacities that are primitive—for instance, hunger, thirst, the sex drive, perception, and intentional action. In the last chapter I described some of the neurobiological details about how brain processes cause conscious feelings of thirst. But in explaining how brain processes can cause feelings of thirst, we have already explained how brain processes can cause forms of intentionality, because thirst is an intentional phenomenon. To be thirsty is to have a desire to drink. When the angiotensin 2 gets inside the hypothalamus and triggers the neuronal activity that eventually results in the feeling of thirst it has eo ipso resulted in an intentional feeling. The basic forms of consciousness and intentionality are caused by the behavior of neurons and are realized in the brain system, that is itself composed of neurons. What goes for thirst goes for hunger and fear and perception and desire and all the rest. Once we demystify the problem of intentionality by removing it from the abstract, spiritual level down to the concrete level of real animal biology, I do not believe that any unsolvable mystery remains about how it is possible for animals to have intentional states. If you start with such simple and obvious cases as hunger and thirst, intentionality is not at all difficult to explain. Of course, beliefs, desires, and sophisticated forms of thought processes are more complex and more removed from the immediate stimulation of the brain by the impact of the environment than are perceptions or feelings of hunger and thirst. But even they are caused by brain processes and realized in the brain system.