Kantians may in turn be skeptical about all such projects, and whether anything deserving to be called either 'morality' or moral 'reasons' could ever be got out of them. A long philosophical tradition claims that there are powerful reasons to meet the requirements of morality, reasons that are necessarily connected with being a rational agent at all, and hence that conduct which violates moral principles necessarily constitutes a significant failure of rationality (even if we don't customarily apply to it the term 'irrational'). Kantian ethics does not need to apologize for adhering to that tradition.

Kantian Ethics (2008) - Ch. 1. Reason