If atheism is true, it is impossible to waste one’s life. You can live for hedonism or altruism, but neither way is more wasteful or virtuous in the grand scheme of the universe. You can try to save the planet or destroy it, but neither is a more wasteful or virtuous way of living now.
Here’s why. In order to argue that a person should not waste one’s life, a person first has to assume a number of things which a naturalistic worldview cannot rationally provide. (A naturalistic worldview holds to the belief that there is no God, no supernatural, no Creator).
Here’s just two of the things required for us to coherently claim that a person is wasting their life:
First, one has to assume an objective morality.
To assess the actions of a person and say that one way of living is virtuous (saving the planet; feeding the poor) and another way of living is wasteful (destroying the plant; starving the poor) one must have some kind of standard that transcends human preference and opinion. We must have a real standard outside of ourselves to coherently assess moral values and actions and not just an agreed upon human standard of what we think is wasteful. If don’t have a real and legitimate standard to appeal to, all we have is preference and opinion and those who have the loudest voices or the power win and get to decide what is wasteful or virtuous. The result is nihilism. There is no right or wrong way to live. But if there is no right or wrong way to live, then there is no coherent way to speak about wasting one’s life, because one must assume a right or wrong way to live in order to claim that a person is wasting one’s life.
(Granted, I have never met an atheist who lives this as though nihilism were true. But I think that is because no is able to live out a false-to-reality worldview consistently. As others (Schaeffer especially) have argued, there is always some point where a false-to-reality-worldview is unlivable in practice. The fact that a particular worldview cannot be lived out is a clue to the fact that such a position is NOT true to reality—it is not true because it is impossible to be lived out. Thus, I would argue that the inability to live out a nihilistic worldview shows that it is not true. We don’t live in universe void of objective moral values, but one where objective moral values exist [objective in the fact that they are real, valid, and binding on all humans regardless of human opinion—subjective in the sense that they come from God who is the source of all goodness and truth]. Deep down we all this is true, even if we claim to believe the opposite. When push comes to shove and someone wrongs us, we can’t help but appeal to a standard that transcends human opinion, even if we claim all morality is human subjective).
Second, for us to speak about the evil of wasting one’s life, one has to assume the objective value of a life well lived.
If this value is not in place, it would make no sense to speak against wasting one’s life! But an atheistic worldview cannot coherently provide this type of value either. In a naturalistic universe there is no value to human life—we are accidents of impersonal evolutionary forces.
In the end, atheism cannot coherently provide us with the foundation necessary to speak about “wasting one’s life.” If atheism is true, there is no such thing as wasting one’s life or using one’s life well. Nihilism rules, or one is speaking incoherently. (We might even argue that one who holds to a naturalistic perspective and speaks out against ‘wasting one’s life’ is employing a form of irrational mysticism—mystical in the sense that it is not based on truth, but just feelings disconnected (even opposed) to the facts of a naturalistic worldview).
Perhaps, then we must reckon with the fact that we all do think it possible to waste one’s life. Where do we get the necessary preconditions (objective morality, objective value of human life) that can give us a foundation to speak against wasting one’s life? I would argue that only the Christian worldview can do this. God exists and has created us for His good purposes; objective moral values exist and come from God, which allows us to us to legitimately and truly know what is right and what is wrong—He has given us access to this information through His Word, the Bible; our value as humans comes from outside of us and intrinsic to us since we are made in God’s image—this means life is precious and should be well spent and not wasted.