However, when weighing the pros and cons of some potential use of U.S. military force in a distant land, we tend to credit our good intentions as if they had been realized. One lesson of recent interventions is that, even as the world’s greatest superpower, we aren’t very good at these things. We squeezed Iraq’s economy for a decade between the two Persian Gulf wars. How many innocent lives did that cost? Developments in military technology — such as drones — make intervention less costly in blood for us and thus possibly make it easier to contemplate. They do little to change the equation for the people we are sincerely trying to help.

Intervention never will be, and maybe never should be, an all-or-nothing decision. There are goals that are worth attempting, but may not be worth giving our all for.

We will never have logically consistent rules about such things (to the frustration of people, including me, who tend to equate logical consistency with justice and good sense). To questions like, “Why Iraq but not Iran?” or, “Why are we standing by while a Syrian dictator tears apart his own country?” the answer is, “Just because.”

Decisions about using force will always be affected, if not determined, by extraneous factors. Is it an election year? How is the economy? Have there been a lot of these situations lately? All these considerations affect a decision whether to use military force even though they have nothing directly to do with it.