The objectivity of ethics and the unity of practical reason

Abstract This article revisits the evolutionary debunking arguments advanced by Katarzyna Lazari-Radek and Peter Singer. It evaluates their implications for the objectivity of ethics and the unity of practical reason. Building on Sidgwickian rational intuitionism, the paper contrasts the stability of utilitarian reasons with the vulnerability of egoistic justification once evolutionary and metaphysical assumptions about personal identity are examined. It further incorporates revised views on free will, moral epistemology, and peer disagreement, arguing for a more sceptical and collaborative philosophical method. The conclusion advocates prioritizing ethical epistemology and moral psychology over continued disputes between major normative theories.