How can rationality be defined?
For the purposes of this discussion I will take one definition from a respected academic in this field. Jonathan Baron in his book "Thinking and Deciding" [Jonathan Baron, Thinking and Deciding, Cambridge University Press 1994] chooses to define being rational as
"the kind of thinking we would all want to do, if we were aware of our own best interests, in order to achieve our goals."
He then goes on to categorise thinking as being about decisions, beliefs or about the goals themselves.
Language and choices of definitions of its words can of course be highly subjective matter but I find this definition particularly inadequate because the choice of goals is entirely left to irrational and subjective choice and can easily be wrong. For example my goal could be to justify the equation 1=0 for which I would have to use very irrational arguments. If we build in the requirement that the goals are being, or have been, rationally set then we have a circular definition where any irrational goal would lead to completely irrational thinking which might, for example, be quite illogical. Then, this type of thinking would reinforce the irrational goal!
We cannot use this as a definition- at least until we have some clear refinement of it. Baron acknowledges this further on
"When I argue that certain kinds of thinking are "most rational" I mean that these help people fulfil their goals. Such arguments could be wrong. If so, some other kind of thinking is most rational."
If we are to understand from this that people means any person and therefore any goal then we still have the same problem. However, his arguments make sense because they appeal to the fulfilment of goals that people generally have. In other words if he uses the word people here to mean people in general then rational thinking is defined (at least in so far as goals are set) as being what people generally do.
This is a fairly major weakness in this attempt to define rationality in purely objective terms. You cannot describe rational thinking and forget that the criteria are themselves a matter of value judgement, such as the judgements made when setting goals. If one leaves the subjectivity of such value judgements in place then the objective approach fails.
Taking Barons definition of rational from a different angle we could well ask what does it mean to be "aware of our own best interests"? This, in contrast to the above description, presupposes that there is such a thing as best interests, which for all intents and purposes we can take to include the goals we set. This is closer to the position I shall take. There are such things as our own best interests, which include what our goals should be. We may not know perfectly what they are but we must assume that they are there, for without them any attempt to define rationality is self-defeating.
The goals we set, and therefore the very definition of rationality is governed by moral choices - by what our goals should be.
"Unlike many other fields of psychology, such as the study of perception where the emphasis is on "how it works", Much of the study of thinking is concerned with how we ought to think, or with comparing the way we usually think with some ideal."
The study of thinking is the area in which the Is-Ought problem is closest to being resolved. For to study thinking we must study what is good thinking. The Is-Ought problem can be stated as "It is impossible to infer, by any logical means, a normative statement from a descriptive statement." i.e. you cannot infer from any statement of the form "A is the case" the conclusion that "John ought to do X. i.e. "Is" and "Ought to" . If we want to break out of this we must make value judgements. Using statements of value we can infer normative statements. For example, If I said "It is raining outside. Therefore you ought to take an umbrella." it would be an illogical inference. However, if I say "It is raining outside. It is good for you to avoid getting wet by taking an umbrella. Therefore you ought to take an umbrella." it is clear that the 3rd statement follows from the first two. The Is-Ought problem can therefore be seen as a matter of value judgements; how do we judge that something is good for someone - or for ourselves?
In these pages I am attempting to map out the solution to this problem by asserting that there are aspects of the way we think which we are morally responsible for - there is good thinking and there is bad thinking. There are ways of thinking that you ought not to indulge in and ways of thinking that you ought to adhere to. Once we have an 'ought to' statement accepted then it is possible to derive many other ought to statements and we have a consistent 'rational' framework for a system of moral guidance.