We see nonviolent social movements forming and acting all around us right now: Charlottesville, Boston, Phoenix. There’s also a lively debate about whether nonviolence is the best response to threats like the alt-right, and if so, why. (Is nonviolence a moral principle, a strategic choice, or both?)

A characteristic aspect of any nonviolent movement is sacrifice. Participants sacrifice by renouncing consumer goods, by contributing money, by spending evenings at rallies, by putting their bodies in harm’s way, by going on hunger strikes, or even by choosing to die before onrushing tanks.

In Stride Toward Freedom, Martin Luther King describes the “laborers and domestic workers, many of them well past middle age,” who had to “trudge” as many as 12 miles each day to sustain the Montgomery Bus Boycott. King writes, “They knew why they walked, and the knowledge was evident in the way they carried themselves. And as I watched them I knew that there is nothing more majestic that the determined courage of individuals willing to suffer and sacrifice for their freedom and dignity.” The words “suffering” and “sacrifice” create a leitmotif in the book as a whole.

Sacrifice deserves scrutiny because it is powerful. Occasionally it shakes the conscience of opponents. More often, it persuades enablers of the current regime and bystanders to take the insurgents’ side. It demonstrates Worthiness, Commitment, and Unity, three of the four assets of any social movement, according to Charles Tilly. (The fourth asset, Numbers, is necessary to make a sacrifice effective.) Yet sacrifice is not always appropriate or valuable. Critical analysis is necessary.

Before we can analyze the kind of sacrifice that is evident in nonviolent movements, we need a serviceable definition of it. Some characteristics of non-violent political sacrifice also arise in other contexts. For example, soldiers make sacrifices that are (in certain respects) just like those of nonviolent protesters. Gandhi was once asked whether his “activities [could] be described as war.” He says he “had no hesitation in replying, ‘Our struggle has all the attributes of a war.’” Yet his nonviolent campaign surely differed from an actual war in more than just its refusal to use physical violence. Thus we need a relatively precise definition of the phenomenon.

I posit that the category of sacrifice found in nonviolent social movements (but not necessarily there alone) has four features.

1. It is concerned with public–social or political–issues. If you give up your career to care for a sick relative, that is a sacrifice but not of the relevant kind.
2. It has a real cost to the one who sacrifices. If you boycott a good that you didn’t like anyway, or for which there are easy substitutes, that is not a sacrifice, even though it might be a politically effective act.
3. The cost is concentrated on the one who sacrifices. If you blow yourself up on an airplane, along with all the other passengers, that is a political sacrifice, but not the kind offered in nonviolent social movements.
4. The act of sacrifice is performative and communicative. A relevant audience must understand that you are sacrificing for a given cause. They must recognize your intention and objective and the cost that you bear.

This fourth criterion goes a long way toward explaining why sacrifice is powerful. It is a form of rhetoric. When you voluntarily bear a steep cost, you provide compelling reasons for observers to draw the following conclusions: you sincerely care about the issue; you and the others who join you are willing to act and will not be easily ignored; in contrast to a violent actor, you are likely to respond positively to reasonable concessions; and you have a perspective that should at least be considered by anyone who wants to understand what people believe about the issue.

These reasons fall short of an actual justification of your position. You could have a sincerely held perspective that is unjust. However, the sacrifice draws attention to your voice and clears away certain barriers to being heard, such as the assumption that you are insincere or unserious. Sacrifice thereby creates the opportunity to offer actual justifications. King writes, “nonviolence comes in as the ultimate form of persuasion. … We will try to persuade with our words, but if our words fail, we will try to persuade with our acts.”

Various complications arise for this four-part definition. For one thing, even if sacrifice always has a cost, that doesn’t mean that the impact on the sacrificer must be a net negative. Gandhi holds that “a life of sacrifice is the pinnacle of art, and is full of true joy.” This aphorism comes amid his summary of the metaphysics of the Bhagavad Gita, according to which “the world cannot subsist for a single moment without yajna [sacrifice]” and “the body, therefore, has been given us, only in order that we may serve all creation with it.” Gandhi also holds that worldly entanglements prevent equanimity, so sacrificing them is the way to avoid distress.

These arguments are rooted in specific religious and philosophical traditions, but people from a wide range of cultures and faiths have experienced joy while making political sacrifices. King observed workers walking miles to work with their heads held high because they were part of a boycott that was part of a movement for dignity. Although walking for miles is a sacrifice, it can bring more satisfaction than discomfort, even during the march. A week in jail with one’s comrades can be a time of solidarity and inspiration even though one’s liberty and comfort have truly been taken away. I think a sacrifice is still a sacrifice even if the net impact on the actor’s utility happens to be positive. This balance may be rare, but the definition of sacrifice does not require feeling more unhappiness than happiness. If it brings joy, so much the better.

Another complication is that it is very difficult to bear all the costs of a sacrifice oneself. In Stride Toward Freedom, King subtly but pervasively traces the impact of his actions on innocent others, starting with his own family. He says that he “gradually lost [his] role as husband and father” because of his activism. His father fell “into a state of constant terror,” and “mother too had suffered,” even taking to her bed under the strain that Martin Jr. was causing. “I was worried about their worry. I knew that if I continued the struggle I would be plagued by the pain I was inflicting on them.” Years after he wrote these words, when he was finally assassinated, his family were again the ones who bore his loss–along with concentric circles of people who had loved him, extending to millions of human beings. Anyone who is cared about causes collateral damage by sacrificing herself. I think a reasonable definition of nonviolent sacrifice should encompass acts that distress the innocent, even though it must exclude intentional efforts to harm opponents.

A third complication is that violent acts can work just like nonviolent civil disobedience under certain circumstances. Gandhi often analogizes satyagraha campaigns to battles. In the Gettysburg Address, Lincoln eulogizes the men who “gave the last full measure of devotion” by sacrificing their lives on a literal battlefield. We know that they were trying to kill their enemies while surviving to fight another day. However, in contrast to almost all martial speeches, the Gettysburg Address never mentions the Union victory or the Confederate defeat; apart from one use of the word “fought,” it is all about suffering, not winning. Pointedly, Lincoln refuses to differentiate between the sides. He converts a bloody battle into an act of pure self-sacrifice, as if the casualties had died while turning the other cheek. The result is effective rhetoric for the same reason that an act of civil disobedience is persuasive. Lincoln presents the soldiers’ sacrifice as a call to our conscience. This is a borderline case, about which readers may disagree, but I am inclined to think that Lincoln successfully expands the category that we are considering so that it includes violent conflicts, as long as they are interpreted as shared sacrifices in the common interest.

At this point, we have a rough, four-part definition of nonviolent political sacrifice. We can also see why it is often effective. It serves as a powerful form of persuasion and it sculpts the soul. King holds that “unearned suffering is redemptive. Suffering, the nonviolent resister realizes, has tremendous educational and transformative possibilities.” King proceeds to quote Gandhi to reinforce this point.

With this definition in hand, we can also consider whether nonviolent political sacrifice is always praiseworthy. I think it is not.

For one thing, the costs transmitted to others can be too high. In a section of his autobiography entitled “Quickened Spirit of Sacrifice,” Gandhi recalls that an American salesman talked him into buying a life insurance policy for the sake of his wife and children. Gandhi’s decision to buy the insurance demonstrated his own “mixed desire. The spirit of self-sacrifice was tempered by the desire to lay by something for the future.” But then his “outlook changed” and he decided that everything he did should be “in the name of God and for His service.” Gandhi stopped making the insurance payments, reasoning that his brother could care for his family if he died, and that, by purchasing insurance, he had “had robbed [his] wife and children of their self-reliance.  Why should they not be expected to take care of themselves? What happened to the families of the numberless poor in the world? Why should I not count myself as one of them?”

Note the way that Gandhi’s “self-sacrifice” is strictly borne by his wife and children. He never hints that the insurance payments undermined his ability to lead a nonviolent movement; rather he sacrificed his family’s income security because he wanted to purify his own stance. In the same book, Gandhi recalls that he “did not hesitate to sacrifice” his children’s literary education in the interest of having them remove human waste from the house and walk five miles each day to his office and back. “My sons have therefore some reason for a grievance against me. Indeed they have occasionally given expression to it, and I must plead guilty to a certain extent. … But I hold that I sacrificed their literary training to what I genuinely, though may be wrongly, believed to be service to the community.” Even if Gandhi’s decision was right, this case is close enough to make the point that sacrificing others is not always justified. A more famous Gandhian example is his unilateral decision to become celibate, although married.

Even if one could bear 100 percent of the cost, sacrifice might not be ethical. Imagine a person with no friends or family who dies in a hunger strike. There is no damage to innocent third-parties, but the sacrificer has destroyed her own life. A utilitarian calculus holds that every life counts the same, including one’s own. By that standard, the sacrifice is ethical if, but only if, it does sufficient good to outweigh the death. Other philosophical traditions (notably, Kantianism) go further and assert that we have duties to ourselves. It could be wrong to squander oneself in a political cause.

But sacrificing not only oneself but others whom one loves can be precisely the right thing to do, as I explore in this post on the Little Rock school desegregation case. Indeed, causing the ones you love to suffer can be one of the most potent and transformative strategies available to the poor and oppressed.

See also: the question of sacrifice in politics; self-limiting popular politics; a sketch of a theory of social movements; and taking satisfaction from politics in the face of injustice. Citations from: Martin Luther King, Jr., Stride Toward Freedom: The Montgomery Story (1958) (Boston: Beacon Press, 2010); Veena R. Howard, Gandhi’s Ascetic Activism: Renunciation and Social Action (Albany: SUNY Press, 2013) , p. 75; M. K. Gandhi, The Message of the Gita (Navajivan Publishing House Ahmedabad, 1959), pp. 17, 15; M. K. Gandhi, An Autobiography Or The Story of My Experiments with Truth, translated by Mahadev Desai, Navajivan Publishing House, Ahemadabad, 1927, pp. 315-6, 374.