5 - Rational Belief and Desire

Summary

AGENTS

To make decisions, agents must have a range of capabilities. Firstly, they must have an ability to represent, and discriminate between, different possible features or states of their environment. Secondly, they must be able to perceive or infer the presence or absence of these features, i.e. to form beliefs about the world. Thirdly, they must be able to compare these possible features or states according to some standard of value – i.e. be able to judge whether they are more or less desirable. And, finally, if they are to be capable of not just thinking about the world but also acting on it, agents need to be able to determine what options they have, to evaluate them and to exercise them. In summary, they must be able to identify both the possible states of the world and their options for changing them and to form cognitive and evaluative attitudes towards both.

This list of conditions may seem quite demanding, but it should be borne in mind that there is no requirement that these judgements be at all refined or detailed, or even that they be conscious. So even cognitively quite primitive entities may well have most or all of the required capabilities. Consider a thermostat, for instance. It inarguably represents features of the world – the temperature – and judges which of these states in the actual one. It also has a crude value system that can be summarised as: cold is bad, warm is good. The actions available to it – switching the heating on or off or doing nothing – are chosen in the light of information it receives about the state of the world and implicitly in view of the consequences of selecting the action.

On the other hand, the way the thermostat makes decisions, if one is happy to speak in such terms, lacks a number of the essential characteristics of human decision making. Although we might say that the reason why the thermostat switches the heating on is that the room is cold and that by doing so it will warm up, the reason we refer to is not the cause of the thermostat's switching on. The thermostat does not itself make the judgements about what would happen if it performed one or other of the actions available to it.