"Watch your posture! Stand up straight!" Maybe you've never had to balance a cup on your head, but chances are pretty good that you've been reprimanded for your posture. We all have. And that's not bad: good posture has all kinds of advantages, like better health and a more confident appearance. We take all kinds of cues from posture.

That's why it's yet another one of our archetypal figures of speech. We live in bodies, which means that, like fire, water, and mountains, they're a readily available tool for making sense of the world. "Stand up for what's right!" "Don't take that lying down!" "I'm head over heels <3" "Keep your chin up!" "Over my dead body." These expressions all mix the literal and the figurative: just because you're discouraged doesn't mean your chin is literally pointing down. But we know what that means.

We Won't Stand For What You Stand For

Dr. King loves these deep, primeval metaphors, and rightly so: they retain their intuitive power even though we've all heard them a gazillion times. And he puts them to use in "Mountaintop." Observe:

Because if I had sneezed, I wouldn't have been around here in 1960, when students all over the South started sitting-in at lunch counters. And I knew that as they were sitting in, they were really standing up for the best in the American dream and taking the whole nation back to those great wells of democracy, which were dug deep by the founding fathers in the Declaration of Independence and the Constitution.

If I had sneezed, I wouldn't have been around here in 1962, when Negroes in Albany, Georgia, decided to straighten their backs up. And whenever men and women straighten their backs up, they are going somewhere, because a man can't ride your back unless it is bent. (36.2–3, 38)

In the first paragraph, MLK plays on the fact that our usual bodily metaphor for asserting ourselves, "standing up," is a perfect mismatch for what sit-ins actually are. It's not a trick: you sit.

In the second paragraph, instead of a contrast between sitting and standing, we have a contrast between hunching over and standing up straight. Standing up straight suggests health, pride, strength, and assertiveness. Hunching over suggests tiredness, weakness, and submission, which is partly why the image of someone riding on the bent backs of Black people harks back to slavery.

Slaves literally bent their backs in the fields all day, and they figuratively bent over backward doing all kinds of work for their masters. Also, to be ridden by someone means to be pushed around, and to be carried by someone is to be supported by them, just as white slave-owners were supported by the wealth produced by Black slaves. Even after slavery ended, Black people, especially in the South, couldn't get white people off their backs. You know what that means.

So they had to stand up.

What makes this image so vivid is that it's literally true that someone has a much harder time riding your back when you stand up straight. You either have to throw them off or go down yourself. And that, ladies and gentlemen, is how the Civil Rights Movement happened.