Applied ethics examines specific practical moral issues arising in fields such as medicine, business, and technology. A classic entry into this domain is the trolley problem, introduced by Philippa Foot in 1967 and expanded by Judith Jarvis Thomson. The scenario asks whether one should divert a runaway trolley to kill one person instead of five, while the footbridge variant asks whether one should push a large person off a bridge to stop the trolley. Most people find the footbridge case less permissible, revealing a moral difference between doing harm and allowing harm. Utilitarians would typically divert the trolley to save five lives, demonstrating how consequentialist logic can conflict with deep intuitions about directly using a person as a means. Related to these scenarios is the doctrine of double effect, which holds that causing a harmful side effect may be permissible when it is foreseen but not directly intended, whereas causing the same harm as a direct means is not.
In the medical realm, bioethics addresses issues arising from advances in biology, medicine, and biotechnology. Beauchamp and Childress articulated four principles that remain central to the field. Autonomy requires healthcare professionals to respect patients' rights to make informed decisions about their treatment. Beneficence requires actively promoting the well-being of patients. Non-maleficence, encapsulated in the phrase "first, do no harm," prohibits actions that cause unnecessary harm. Justice requires fair distribution of healthcare resources. Informed consent operationalizes autonomy by ensuring patients voluntarily agree to procedures after being informed of risks, benefits, and alternatives. The ethical debate around euthanasia centers on whether individuals possess a right to die with dignity, with supporters appealing to autonomy and compassion and opponents citing the sanctity of life and the risk of abuse. Active euthanasia involves deliberately causing death through acts such as lethal injection, whereas passive euthanasia involves withdrawing or withholding life-sustaining treatment.
Emerging technologies raise novel ethical challenges. Genetic engineering prompts concerns about designer babies, consent of future persons, equity of access, biodiversity risks, and the moral status of gene editing technologies such as CRISPR. Cloning raises similar worries about human dignity, the commodification of life, and the psychological impact on cloned individuals. Organ transplantation involves challenges of consent under opt-in or opt-out systems, the fair allocation of scarce organs, the definition of death, and the ethics of organ markets. Artificial intelligence raises issues of algorithmic bias, privacy, accountability for autonomous decisions, job displacement, and the transparency of automated decision-making. Across all these domains, applied ethics draws on the foundational theories but adapts them to the often messy, context-laden realities of practical decision-making.