And Samson grasped the two middle pillars on which the house rested, and he leaned his weight against them, his right hand on the one and his left hand on the other. And Samson said, “Let me die with the Philistines.” Then he bowed with all his strength, and the house fell upon the lords and upon all the people who were in it. So the dead whom he killed at his death were more than those whom he had killed during his life (Judges 16:29-30)
The dictionary defines suicide as the intentional taking of one’s own life so one might say that inasmuch as Samson intended the house to fall and was aware that he would die when the house fell that his action falls under that definition of suicide. But this doesn’t tell us a lot about the morality of the situation.
Compare two scenarios. In the first scenario a man, for whatever reason, decides to end his life so jumps in front of a train. In the second scenario a man, seeing two children in danger, jumps in front of a train to push them out of the way. In both scenarios the man knows with a fair degree of certainty that he is going to die. In both scenarios the man is the cause of his own death and in both scenarios his action is intentional. And yet we can see a moral difference between the two scenarios. The first scenario seems to be a purely selfish act – the man is only concerned with himself. The second scenario is completely selfless act.
We can think of many examples that are like the second scenario. The crew of a sinking ship that let the women and children into the lifeboats ahead of them. The scientists who battle to end to prevent a nuclear melt down. Those who tend to those with infectious diseases. These selfless acts, where someone lays down their life to save another would not usually be called suicide. The moral difference seems to be that in these cases the primary intention is not to die but one is nevertheless prepared to die to achieve the desired end.
Greater love has no one than this, that someone lay down his life for his friends. (John 15:13)
Judged by this standard, Samson did not commit suicide but rather acted in a way which involved his own death to achieve some other goal.