What would it take for you to willingly sacrifice your life? Or to take someone else's life? In wars, people do both. Why? What does it take to convince large numbers of people that dying and killing are worthwhile? One might think it only requires someone giving an order, but there are many cases of people refusing to fight: many American college students during the Viet Nam war, for example. When called upon to fight and die for their country, sometimes people comply. But sometimes they walk away, or join the other side.

Determining why is in part a problem of ideology, in the second sense of the word as "cultural common sense."