"This attitude [the abstract method in mathematics] can be encapsulated in the following slogan: a mathematical object is what it does."

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When you fight, you don't fight for abstract values like the flag, or the nation, or democracy. You fight for your buddy. You fight to keep him alive, and he fights to keep you alive, and you go on that way, day after day, battle after battle. And when one of your buddies dies, something inside you dies as well. But you go on. You fight, so that his death isn't meaningless, his sacrifice isn't for nothing.

— Richard Marcinko