Here’s an unexpected demonstration of the power of philosophy, even amongst those completely oblivious to it. In this video, a rather ditzy vegan girl addresses the charge that vegans and vegetarians are guilty of killing tons of wild animals in the process of planting and harvesting crops. (It’s true!)
The doctrine (or principle) of double effect is often invoked to explain the permissibility of an action that causes a serious harm, such as the death of a human being, as a side effect of promoting some good end. It is claimed that sometimes it is permissible to cause such a harm as a side effect (or “double effect”) of bringing about a good result even though it would not be permissible to cause such a harm as a means to bringing about the same good end. This reasoning is summarized with the claim that sometimes it is permissible to bring about as a merely foreseen side effect a harmful event that it would be impermissible to bring about intentionally.
How does that apply here? According to ditzy-vegan-girl, it’s morally okay to do something wrong (like killing animals) as an unintended side effect of pursuing a good end (like eating veggies) but not okay to do that same wrong thing (killing animals) as a direct means to your ends (like eating meat).
Of course, the doctrine of double effect doesn’t actually help her answer the moral charge here. The doctrine is a handy tool of rationalization for people with ethics so disconnected from reality that they simply must violate them to live. It’s not a real ethical principle.
Ditzy-vegan-girl surely hasn’t ever heard of the doctrine of double effect, yet she’s using it all the same. That’s the power of philosophy.