The question is rhetorical, in that the implied answer is obvious. Whose life is it...... Mine (of course). Freedom of choice means I can choose for myself, including the choice to die on my own terms. I think for many in our culture this is reflexively seen as true and good. Autonomy is a treasured value.
Paul writes, "We do not live to ourselves, and we do not die to ourselves. If we live, we live to the Lord, and if we die, we die to the Lord; so then, whether we live or whether we die, we are the Lord's." (Romans 14:7-8, NRSV)
I consider this to be the Kingdom of God answer to the question, while the other is "the Eden Option." In other words, the serpent asks Eve (and by extension Adam) "whose life is it anyway?" The correct answer is "the Giver of Life," it is God who made me and owns my life. The (sinful) human desire is to say, "Mine."
Autonomy is wonderful, but in reality it is only part of the story. The "Objective Reality" is that we are dependent creatures. (note, the word creature implies a Creator) We at not self-generating and we are not rulers of anything (including ourselves, I believe). Paul is not arguing his point here, he assumes it is obvious and it is part of a larger argument about tolerating different views of the Jewish dietary practices.
Each of us must answer the question, "Whose life is it anyway?" The answer is fundamental to our life.