fifth edition (revised) 1996, Princeton University Press, first paperback printing 1971; chapter 24, section I, p. 225. Full text on archive.org.
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' [italics his]. 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 most problems of importance. 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 attain something like objectivity.