Hypothetical: We breed a species of cow smart enough to consent to a contract. It agrees to give us milk. Is this milk now vegan?— Zach Weinersmith (@ZachWeiner) August 13, 2014
Zach Weinersmith, the webcomic artist responsible for Saturday Morning Breakfast Cereal, offers this original ethical question. Vegetarians eschew meat for various reasons, often to avoid harming animals. Vegans often take this perspective even further by using nothing which exploits an animal. So a vegan may choose to not drink milk or use sheep wool because those are products extracted from animals, even though the animals are not killed.
How would you answer Zach's question?