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It is impossible to know his motive when jumping on a grenade. If, as halcyon pointed out, his goal was to reduce his pain and thereby increase his net happiness, he is clearly a hedonist. Perhaps the idea of living with survivors guilt was the impetus behind his actions, in which case his fear of emotional pain and unhappiness propelled him to such measures.
Suppose he had other intentions, such as posthumous heroism. In that case, his narcissistic and egotistical mind was the impetus behind such actions. Although he wouldn’t be around to see it, the very idea of being considered at such an elite status was enough cause for him to jump on a grenade. His life revolved around pleasure to such an extent that he followed it to the end and his hedonistic nature was what actually killed him.
Either way, I’d say he’s definitely a hedonist and there most certainly were calculations involved in his decision.</p>