What is the significance of the way finny dies?

Finny is a casualty of war, without ever having been involved in battle. Brinker says this, and Dr. Stanpole reiterates it; but it is not the same kind of war that Finny is really a victim of. He is a victim of a sort of internal war, against yourself, that lashes out against others. Gene hurt Finny because his jealousy and carelessness and his "savage" nature took control of him; Gene didn't hurt himself in trying to get his good nature to win out over the bad, someone innocent was harmed in this struggle. Just as Finny is a victim of Gene's war, so many people turned out to be victims of someone else's war too; perhaps this is why Dr. Stanpole and Brinker see Finny as a war casualty, because his situation is very similar to theirs.