Rational and reasonable… I’ve been wrestling lately with these words (and they’ve been winning).
I’m trying to distinguish meaning between them, as they’re typically used. For instance, could they be construed as synonyms? Or is rationality a function of reason? Contrastly, I doubt that reason is a function of rationality, however.
And, assuming they are different in some important, fundamental way, a follow up question is:
Is it always rational to be reasonable? And Is it always reasonable to be rational?
“could they be construed as synonyms? Or is rationality a function of reason?”
They could (and often are) construed as synonymous, but I don’t think they are most usefully interpreted so. It is useful to describe rationality as a function of reason.
The most telling example is Hume’s irrationalism. He accepted that the external world and the enduring self are irrational (principally through the fallacy of induction). So in a strict philosophical sense, the concepts were ‘against reason’. However he would not accept pyrhonnian scepticism. Although acting as if the external world exists is irrational, he claimed we still do so through customary human nature.
So, if this naturalism of Hume is emphasised (As it has been for most of the 20th century), then the way ordinary humans act can be seen as a justification for so acting. It is ‘reasonable’ (in a less-philosophical sense) to follow human nature and believe in an external world rather than to live the life of pyrrho.
Thus, a useful distinction between the rational and the reasonable.