The degree to which Man is, can or ought to be rational has long been a favorite question of philosophers, psychologists, sociologists, economists and barflies alike. No one minimally acquainted with the infinite variety of human self-destruction, without at least one or two episodes of which almost no human life seems ever to be got through, can doubt that irrationality is, at the very least, quite common. Man may be the only rational animal, but only sometimes or intermittently.
Rational action can only be that which conduces, on some mixture of evidential and logical grounds, to a desired goal. But goals themselves are not rational, except in so far as they are subordinate in a hierarchy of goals and their fulfillment conduces to that of the highest goal of all, whatever it might be. But what cannot be rational cannot be irrational: so that desires, at least ultimate ones, are not irrational, they are arational.