Can a Choice Be Rational Without a Common Scale?

Suppose one job pays more but leaves little time, while another pays less yet offers greater purpose and freedom. It is tempting to assume that enough information would let us convert every gain and loss into one total score. Yet salary, purpose and freedom may have no common unit. Philosophers call this difficulty value incommensurability.

Joseph Raz illustrates the issue with two successful careers, one as a lawyer and the other as a clarinettist. Neither need be better or worse, but they need not be exactly equal either. Ruth Chang argues that some options which fit none of those three relations may still be ‘on a par’, so they are not wholly incomparable. This is a contemporary dispute, not a proved theorem. Other philosophers hold that apparent incommensurability reflects missing knowledge or vagueness in the term ‘better’.

In my view, the absence of a unique ranking does not reduce us to flipping a coin. Reason can still check the facts, exclude options that are clearly worse in important respects, and test which loss we are prepared to accept. The final decision may not discover a highest score that was there all along. Through commitment, it can give one value practical weight in a life. Such a choice can be supported by reasons without pretending that every reason can be added precisely; choosing one option need not make the other worthless.

https://plato.stanford.edu/entries/value-incommensurable/