The collective responsibility that all Americans share is the responsibility of allowing too many people to have too many guns; guns of a kind that no civilian ever needs can be bought in this country by almost anyone who wants one. We have been running an experiment of a kind that no sane ethicist would allow: what happens when, in a country large enough to contain every imaginable kind of crazy, from the inward-turning, maniac sort to the outward-turning, politicized kind, you make sure that almost anyone can readily buy any kind of gun? And now we know the answer: you get more gun massacres than there are days in the year.

No sane person thinks that Carly Fiorina is “guilty” of the shooting at Planned Parenthood, or that Wayne LaPierre is guilty of the one in San Bernardino—but those who put weapons into the hands of anyone who wants them are complicit in what happens when they do. (And those who encourage hate speech directed at health clinics share responsibility for what happens when people take them seriously.) They are responsible in the same way that we are all responsible for the bad consequences of our beliefs, in exactly the same way that Wahhabi imams who preach intolerance are responsible for the consequences of their words. Sometimes you can avoid such horrible consequences with a minimal effort at thinking and acting responsibly. And when you can, you should.

To search for an ideological sorter for these killings—this one is a terrorist, but this one is merely a nut, and this one is sort of a nut and sort of a terrorist—while refusing to do obvious and simple things to prevent them is to be responsible for their perpetuation.