I liked the following argument I made in an online discussion about the existence of the soul and whether atheists can be moral or not:
Let me make several points here which however hard they may be to take are true (and if you have not thought them out Doestoevsky and Nietzsche have). First, it makes no sense for a person to speak of morality who is a determinist. Apart from any consideration of whether the determinist position is correct or not, speaking of what a person ought or ought not to do is clearly meaningless because the person is propelled by outside forces and is not capable of making a decision according to the determinist position. Therefore it is a species of mendacity to protest that a determinist atheist may be moral too, from a determinist atheist point of view, because there are no categories of morality in determinism. Fate neither affirms nor denies moral behavior. Morality belongs to a civilization that believes in human freedom of choice. There is clearly no sense in claiming for determinists that they are moral people too since their very worldview repudiates notions of morality. Therefore it is deceptive mendacity to say that they are moral except if one is operating with the assumption of human freedom, and should a determinst argue this why should it not be supposed that they may also be lieing in the supression of the recognition of the authentic categories of moral perception in their core beliefs as well since they lie about their affiliation with systems of morality? But this is entirely about the deterministic atheist. It is true to say that not every atheist believes in determinism. Even Epicurus (not entirely an atheist though) introduced a mystical swerve into his account of the nature of atom's freefall to account for human freewill. But the question is, if we are not determined by outside physical causality, if we have real choice and therefore real moral categories, how do we account for these in a purely materialist worldview? To say here that materialists, etc. can be moral people is beside the point. The question is if their worldview accounts for their moral categories, if they have a comprehensible synthesis of human experience, or if they are really foolish and self contradictory as Bernanos charges. In what mysterious way can we hold to human freedom of choice and not circumscribe natural inferences from its essential independence to the ontological reality of the soul? If humans are able to choose morally then they are free. If they are free, then it seems they are independent in a significant sense from material casality at the point of their choice- they are not driven by material causality in their moral descision-making. If they are independent from material causality in such a significant, civilization forming way, then it is plausible that they have souls, that element that governs their bodies that are otherwise driven by material causality.