From the movie "Flash of Genius" about Robert Kearns, the inventor of the intermittent windshield wiper: "I can't think of a job or a career where the understanding of ethics is more important than engineering," Dr. Kearns continues. "Who designed the artificial aortic heart valve? An engineer did that. Who designed the gas chambers at Auschwitz? An engineer did that, too. One man was responsible for helping save ten…
Sometimes the distinction is even more insidious. I did work on perpetual flight for drones, and Facebook had a perpetual flight project that had the goal of bringing internet access to remote locations in Africa. Sounds humanitarian, but I also didn't want to be responsible for subjecting poor Africans to what I consider Facebook's panopticon. Or maybe it would have been a net boon for the region? It's really hard to tell a priori, so the best I have managed for myself is just to try and stay in theory, where developments are further removed from direct consequence.