Since the terms ‘reason’ and ‘rationalism’ are vague, it will be necessary to explain roughly the way in which they are used here. First, they are used in a wide sense; they are used to cover not only intellectual activity but also observation and experiment. It is necessary to keep this remark in mind, since ‘reason’ and ‘rationalism’ are often used in a different and more narrow sense, in opposition not to ‘irrationalism’ but to ‘empiricism’ ; if used in this way, rationalism extols intelligence above observation and experiment, and might therefore be better described as ‘intellectualism’. But when I speak here of ‘rationalism’, I use the word always in a sense which includes ‘empiricism’ as well as ‘intellectualism’; just as science makes use of experiments as well as of thought. Secondly, I use the word ‘rationalism’ in order to indicate, roughly, an attitude that seeks to solve as many problems as possible by an appeal to reason, i.e. to clear thought and experience, rather than by an appeal to emotions and passions. This explanation, of course, is not very satisfactory, since all terms such as ‘reason’ or ‘passion’ are vague ; we do not possess ‘reason’ or ‘passions’ in the sense in which we possess certain physical organs, for example, brains or a heart, or in the sense in which we possess certain ‘faculties’, for example, the power of speaking, or of gnashing our teeth. In order therefore to be a little more precise, it may be better to explain rationalism in terms of practical attitudes or behaviour. We could then say that rationalism is an attitude of readiness to listen to critical arguments and to learn from experience. It is fundamentally an attitude of admitting that ‘I may be wrong and you may be right, and by an effort, we may get nearer to the truth’. It is an attitude which does not lightly give up hope that by such means as argument and careful observation, people may reach some kind of agreement on many problems of importance; and that, even where their demands and their interests clash, it is often possible to argue about the various demands and proposals, and to reach – perhaps by arbitration – a compromise which, because of its equity, is acceptable to most, if not to all. In short, the rationalist attitude, or, as I may perhaps label it, the ‘attitude of reasonableness’, is very similar to the scientific attitude, to the belief that in the search for truth we need co-operation, and that, with the help of argument, we can in time attain something like objectivity.
From The Open Society and Its Enemies Volume 2. Harper Torchbooks 1967.