Altruism—like all our other finest traits—has its roots in Darwinian evolution. The reflex is strongest toward those who carry our genes, especially our own children. In fact, it’s so strong that we don’t even use “altruism” in that case. But biologists have charted this relationship very well.

What humans have done, however, is take many of these basic reflexes and made them much more complex in our minds and in our cultures. Altruism now extends to sacrificing ourselves for abstract things, like country or ideals or to benefit the stranger or all humankind. Lately, with this circle-expanding reflex I call “otherness,” we’ve seen millions become devoted to helping other species, or even the ultimate palpable-abstraction, a living Earth.

This altruistic outwardness is universally respected as a deeply honorable human desideratum. But it gets more complicated, still. Altruism becomes problematic when the giver and receiver of aid disagree! Or when assistance repeatedly does not have the effect promised, but instead wreaks a variety of harms. It can get political, as when millions on the right resent altruistic measures they deem “politically correct” and when millions on the other side disagree over the altruistic intent and effects of pro-life rage.

Can altruism be “addictive?” Almost any mental state can be, we’ve learned. The human brain is spectacularly good at being self-tuned to release chemicals, on demand, that give the individual various kinds of highs. The biggest come from activities and thoughts that most call wholesome, like love, skill, music, and such. But coming up close behind is self-righteousness! When you see someone who is indignant all the time—whether it’s your crazy neighbor or that face in the mirror—look for the flush responses and repetition rates of an addict, coming back again and again for that self-doped “hit.”

And yes, altruism can be one of the top triggers and excuses for self-righteousness. That part is just obvious.

David Brin is a space physicist and science fiction writer, and the author of the chapter “Self-Addiction and Self-Righteousness” in the new book Pathological Altruism.