## TL;DR
The Western ethical tradition is dominated by three approaches: virtue ethics (Aristotle — character), deontology (Kant — duty), and consequentialism/utilitarianism (Bentham/Mill — outcomes). Contemporary ethics integrates elements of all three.

## Core Explanation
Aristotle: flourishing (eudaimonia) through cultivating virtues. Kant: moral worth from acting from duty, treating persons as ends. Utilitarianism: maximizing overall happiness.

## Detailed Analysis
The trolley problem illustrates deontological vs. utilitarian reasoning. Bioethics — informed consent, patient autonomy, resource allocation — draws on all three traditions. Effective altruism represents a modern utilitarian movement.

## Further Reading
- Stanford Encyclopedia of Philosophy (free, peer-reviewed)
- Internet Encyclopedia of Philosophy
- Justice (HarvardX — Michael Sandel)