If one considers the human person simply to be an anatomical system which includes a sophisticated neural subsystem, referred to as a human brain, a subsystem that seems to be capable of reasoning, perception and a kind of self-awareness we call consciousness, then this reduces the human person to something entirely material — a mere assemblage of atoms. Such a vision of the human person cannot address one of the most essential characteristics of being human, having free will and moral responsibility. In such a view of the human person, free will is merely a comfortable illusion.
This is not an unreasonable view of the human person. Quite to the contrary, one can find this perspective in any number of deep philosophical thinkers. No less an intellectual giant than the late Stephen Hawking, Sir Isaac Newton's peer in many ways, who held the same Lucasian Chair of Mathematics at Oxford University, wrote about his view that free will is merely an illusion. It is not real. I would say that this thesis is a fundamental corollary of the view that a human person is merely a dynamic assemblage of atoms.
This corollary follows from the known computability of atomic interactions under all the typical conditions that human beings find themselves in. Given a sufficiently massive parallel computational capability, every atom of the human body, together with all interactions, could be simulated in the context of a typical environment. Apart from known random atomic and sub-atomic effects, every atomic state could be predicted to any desired degree of accuracy to any desired time into the future. It wouldn't matter if it took the computer a billion years to compute a day of human time. This clearly establishes the determinative nature of human behavior, modulo random effects that are irrelevant to actual free will (which entails moral responsibility). In such a scenario, human free will is clearly an illusion.
Thus, for free will to be a reality, the nature of the human person must involve more than atomic composition. Clearly, this argument is not affected by the addition of other physical particals or phenomena, such as muons or anti-particles. Everything is still, at least in principle, subject to computer simulation.
The argument is also unaffected by nonlinear macro phenomena, such as chaotic attraction states, as some have tried to argue, as based on the inherent difficulty of predicting, based upon computation, in the realm of chaotic regimes. Although chaotic phenomena are notoriously difficult to predict, they are not theoretically impossible to predict, barring the presence of random phenomena that effect large outcomes. Even in the latter case, it is still possible to predict a range of possible outcomes, conditioned by random initial and input phenomena. The issue here is practical, not theoretical computability, and theoretical computability is all that is required for our argument.
So where does this leave us? Obviously, if the spiritual dimension of the human person is simply an illusory perception of phenomena that are difficult to understand or predict, but not something fundamentally real, then we have no grounds for concerning ourselves with spiritual growth. Spiritual growth, as such, could then be explained as a purely psycho-dynamic phenomenon, perhaps with a large behavioral and/or cognitive component. This is actually the approach taken by contemporary psychologists, who have attempted to interpret the insights of history's mystics within the framework of known developmental psychological modeling theories. Such phenomena as compassion and gratuitous (unrewarded) generosity are regarded as behavior that can be acquired in much the same way that one might acquire a taste for coffee in a wider social context where these patterns are viewed in a favorable light. In other words, all that is required to understand altruism, in this view, is that it can be acquired as a habit under conditions of a suitable history of operant rewards. Pure Skinnerian theory with a possible admixture of cognitive theories.
Equally obviously, if the spiritual dimension is illusory, then the foundations of human civilization are purely arbitrary. One can be equally unhappy or happy under any kind of social order if one simply grants that none of our behavior is truly our responsibility in any moral sense. Social order in such a case depends entirely upon a system of rewards and punishments that is designed to curb social chaos while enabling an otherwise unfettered expression of human instincts. One may view this a built upon the principles of utilitarianism, if one likes. The evolution of such a system may be very difficult for social theorists to predict, but that is not relevant to this discussion. There will be a natural tendency for any social order to maintain stasis while otherwise minimizing discontent. There is room here for the occasional genius, but any consideration of saints and sinners must be viewed in that context, i.e., as social outliers in a statistical sense, capable of perturbing the system, and possibly exciting new and interesting emergent phenomena, but not capable of establish a "kingdom of God."
Certainly, if the spiritual dimension is illusory, one can base one's own life goals on purely material considerations. Life then becomes a multi-person game, in the sense of John von Neumann's theory of games. One need not concern oneself with acquiring altruistic behavior unless that is what makes one happy, for whatever reason. There is no question of reward or punishment in an afterlife, because there is no ground for belief in an afterlife.
Finally, in viewing social order as following game-theoretic patterns, with rewards and punishments agreed upon ahead of time, if only provisionally, then the natural social outcome may be most stable under conditions of either social relativism or social fundamentalism, whatever makes most people the most happy. There is no reason for social theorists to incorporate issues of morality unless large populations of people prefer to think in that way. It is enough to remain in a purely material theoretical framework in order to satisfy all curiosity. That this happens in practice can be seen from relatively recent attempts to explain altruism via natural selection — i.e. by appealing to an altruism gene. Thus, someone like Mother Teresa need not be explained by appealing to her spiritual history and growing relationship with God. One can simply point to the dominance of her inherited altruism gene. When such a gene can't be found in a saint's genetic history, one can simply appeal to the process of genetic mutation &mdash an appeal that seems plausable given the relative rarity of saints.
It's difficult to think of a more pointless exercise than such a life. We would have to agree with Macbeth,
Life's but a walking shadow, a poor player That struts and frets his hour upon the stage And then is heard no more: it is a tale Told by an idiot, full of sound and fury, Signifying nothing.
Surely, without the spiritual dimension and the hope of eternity in a different created reality, we have nothing to look forward to individually or as a species than ultimate and final death. And this is a major part of the philosophical framework that underlies the petulant perspective of radical existentialism. Existentialists who are mathematically challenged tend to regard free will as a convenient hypothesis, but not primarily as a philosophical ground for responsibility. Rather, free will is often seen as a burden, to be disgarded in favor of radical whim (since that seems to make the writer happy). In other, less petulant, formulations, one takes free will simply to be an exercise of choice (however arrived at) with an obligation to consider consequences in making those choices. Where that obligation derives from is usually not considered in an absolute sense, but rather as yet another convenient hypothesis to satisfy the social consensus. (There may be some philosophical hand waving to make it sound universal, as in Kant's Categorical Imperative, usually taken in its first formulation: "Act only according to that maxim by which you can at the same time will that it would become a universal law.".
No appeal to a spiritual realm is required in such a theory. For an insightful critique of Existentialism, see the chapter on Existentialism in The Handbook of Today's Religions.
Indeed, no amount of a priori philosophizing is sufficient to introduce grounds for a belief in free will. Free will is not a given in a universe governed by mathematical laws. It is something added from the outside. As such, it can only be appealed to on grounds that suppose something beyond the merely physical. But since all knowledge is ultimately reduced to experience (albeit including the experience of infused knowledge), knowledge of a transcendent reality requires input from that reality. In other words it requires revelation in the classical sense. Although one can intuit a creator by appeal to a notion of necessary causality or a notion of ultimate design, intuition of moral will, in a way that distinguishes the underlying phenomena from biological necessity (behavioral development or the altruism gene) and in the perspective that also comes to us from revelation, is quite different, indeed, though the intuition of free, moral will does appear to be universal in human kind, the intuition of itself does not appear to provide rational grounds for its reality. Only revelation can do that, but faith in revelation requires more than mere ratiocination. If it is to rise above the level of instinct or human trust in authority, faith in things that can only be learned through revelation (such as the Trinitarian nature of God or the dual nature of Christ) ultimately requires infused confirmation &mdash the testimony of God in and to the human soul. Moreover, faith in revelation itself as a source of truth requires just such confirmation.
It may be seen in many existentialist formulations that the emphasis on free will is freedom from compulsion. The desire of many is to throw off everything that appears to be a compulsion, whether imposed by the outside (as in coercion), through habit (even addiction), or even through the inner voice of a suspect conscience. Shame, as a source of motivation, is regarded as corrupt because it appears to be pre-logical. But one might as well disregard hunger or thirst, if only outward evidence is to be admitted in the critique of an unfettered reason. Conscience is simply a combination of psychological and spiritual factors weighing in on a moral decision. In its purest form, conscience is the inner voice of the Holy Spirit. Practice in the faith augments this voice with internalized values, principles and imperatives. Practice opposed to the faith obscures this voice with competing desires.
The psychological component arises from the complex interplay of parent and child. When rules are internalized primarily through coercion, these rules take on highly negative cathexis — usually fear. When the rules are internalized primarily through reward of the child's natural efforts to please the parent, the cathexis can be very positive, albeit overlaid with negative features when parental withdrawal of approval, or actual disapproval, is experienced. The kind of fear that may develop here can be wholesome if it isn't the result of abuse, subtle or otherwise, as when disapproval is displayed in abusive anger or in coldness.
Even wholesome fear can come to be regarded as unwanted compulsion in a rebellious teenager who is acting out the inner compulsion to explore forbidden territory.
The ultimate exercise of free will comes in a conscious choice to accept the inner logic of moral compulsion. Thus, when one comes to appreciate the moral imperative to forgive those who hurt us because of a growing realization that forgiveness is a necessity in growing the kingdom of God, one exercises true freedom in the acceptance of the imperative in one's own life. But this is not principally a freedom from compulsion. It is primarily a freedom to accept a kind of moral compulsion that is not compulsory in any purely material sense. In current Christian parlance, we speak of "freedom to" rather than "freedom from". Ultimately, "freedom to" is "freedom to conform one's life to the will of God." This is why the Church has come to recognize the absolute necessity of religious freedom.
It should be noted here that choices which have no particular moral content, such as the flavor of icecream to eat for desert, do not (or at least need not) actually involve free will in this sense. Such choices can operate purely at the level of following desires. The choice to follow one's desires based upon preliminary moral considerations, however, does (or should) involve free will. Thus, we say that social drinking is a positive good, since the good the follows in the form of enhanced social interaction outweighs any negative results (such as killing brain cells) as long as the drinking is moderate. At that point, choosing a flavor of wine or brandy already presupposes the moral issue has been decided..
Thus, it can be seen that both the purpose and the operative regime of free will always involves moral content. The decision of Harry to date Sally may be based upon the fact that he finds her attractive. In that case (and prescinding from consideration of the morality of following that desire), Harry's decision need not involve free will or any moral question once the morality of dating in general is granted, but only the natural flow of instinct. His decision to break a date with Julie in order to date Sally is another matter. His decision to date Sally in spite of her plainness may be an act of kindness, in which case there is moral content in the decision. Likewise, his decision to marry Sally has an obvious moral content. When there is moral content at stake, either free will or the habit of virtue (or both) is involved. Not otherwise.
In practice, however, a decision to date a particular person can easily have deep consequences or meaning that is evident to a spiritually advanced soul, but entirely opaque to a beginner. The Holy Spirit can always intervene in such a case to advise the tyro through the voice of conscience. We would call this an instance of actual grace. The Holy Spirit, seeking a certain outcome for the sake of the dater or the datee's spiritual development, may excite what may be regarded as an instinctive response that seems mystical or otherwise inexplicable. This sometimes occurs in cases of "love at first sight." When this instinct is opposed by prior prejudice or is complicated by a temptation to stay within oneself, a moral decision, and thus free will, is involved. In no case is free will ultimately thwarted by the Holy Spirit, though it may be bypassed, for a time, unbeknownst to the receiver of the desire. Even in such a case, when the attraction remains unexplained and based in mystical experience, the decision to marry will require an exercise of free will.
The distinction I am attempting to explain here is grounded in the distinction we have already recognized between the human soul and the human brain. The human brain is clearly capable of reasoning and making choices apart from its connection with the human spirit. This level of reasoning and making choices is already operative in, for example, chimpanzees. The level of abstraction that principally distinguishes human from animal reasoning may be wholely or partly seated in the human brain. It may also involve a complex interaction of brain and soul. It remains an open question how much of human reasoning can, in principle, be emulated by a computer. As we have seen, only free will in the moral sense (including the choice to accept faith) can truly be known to require a soul for its existence at this stage of our understanding of the human brain.
Consider a massively parallel simulation of a human person's anatomical system, one that is detailed down to the atomic level and so accurate that it can predict any choices that are made entirely within the confines of the anatomy, i.e. with no influence from the hypothetical soul. And suppose that this simulation is coupled with a virtual reality that the simulated system inhabits that is sufficiently detailed so as to be totally convincing to the simulated person. Suppose further that the person is presented with moral choices in the virtual reality.
Suppose further that there is a real person who is being simulated and that person lives in a reality that is perfectly mirrored in the virtual reality of the simulation. Suppose that the real person is presented with the same moral choices the simulated person is presented with. In principle, if the simulation is accurate enough, it should be able to predict the choices made by the real person, if the real person only makes choices within his anatomical system, and it should fail to predict some choices where the person's soul is engaged.
We're almost done, but not quite, because it is possible that there are random elements in the system that mask real choice. A human soul would not make random moral choices, but a purely anatomical "person" might. Without knowing anything a priori about the probability distribution of these random choices, we would first have to measure a long series of choices to attempt to determine any underlying distribution. We would then need to run a number of subsequent strings of similar length to test the probability distribution model accuracy in a kind of Bayesian analysis. These would be compared with the performance of the actual person.
Thus, in theory, we could obtain experimental data that could rule out the anatomical hypothesis, that all choices are explainable purely by the physical nature of the person (i.e., without appealing to a spiritual component.) This would tell us that there is an unmodelled outside influence, and we could certainly be forgiven if we presumed that this is the soul, though it could originate from another spirit entirely.