The idea that man can be destroyed but not defeated from The Old Man and the Sea could be explained or paraphrased as:
- A man can be killed, but as long as he doesn't quit he can't really be defeated.
Santiago goes fishing day after day even though he is on a "losing streak," as we might say today. He hasn't caught a fish for a very long time. He survives only because the boy brings him bits of food. But he doesn't quit. He continues to fish everyday and continues to try. His "spirit" is not broken.
More specifically, Santiago hooks the marlin and does terrible battle with it. He is an old man but he uses his strength and wits to defeat the fish, at the cost of great physical suffering. Again, he doesn't quit. Even after he defeats the marlin and then must fight the sharks, he continues the battle. His spirit remains strong. He doesn't get the fish home in the kind of shape he needed to earn money for it--he fails, technically. But a man who keeps fighting is not a failure.
This is Hemingway's modern view on the warrior. Hemingway is too modern and worldly and intelligent to pull the old cliche of the warrior giving it all he can and being unrealistically victorious. The "good" or "right" or "just" doesn't always win. The knight in shining armor doesn't always carry the day. But Santiago can fight, nevertheless. This makes him noble, like the marlin. And it makes him undefeated.
IT MEANS you can beat him up but in the end he will win.