On Deontology

In lecture two, we turn to deontological ethics, which emphasizes moral principles and rules for action rather than character traits. We consider a range of approaches—from Abelard’s focus on intentions and Aquinas’s natural law grounded in human flourishing, to ethical intuitionism with its plural moral principles, and Haidt’s five-dimensional moral foundations theory. The lecture builds to Kant’s landmark categorical imperative, challenging us to act only on maxims we could will as universal laws and to treat humanity always as an end, never merely as a means.