Tamar Gendler continues Yale's Philosophy and the Science of Human Nature course by finishing her treatment of Kant, laying out the categorical imperative as the requirement to act only on maxims you could will as universal law, and applying it to the duty to keep promises. She then turns to the aim of moral theory before introducing Philippa Foot's Trolley Problem, the classic case pitting the intuition against killing one person against the intuition favoring saving five. Gendler walks through a critique of Foot's own solution and closes with Judith Jarvis Thomson's alternative formulation of the dilemma, comparing the bystander and footbridge versions. Recorded in Spring 2011 as lecture fourteen of the course, the session runs chapter by chapter from Kantian ethics into contemporary trolley-problem literature, giving students both a historical grounding and the tools used in present day moral philosophy debates.