Free will, the ability to choose the course of one’s actions, underlies modern justice systems and the significance of our interpersonal interactions. Intuitively, free will is a fundamental aspect of the human experience, as we feel like the source and manipulator of our thoughts and actions. The increasingly apparent deterministic nature of the universe, however, undermines the basis of these intuitions.
In response to free will and its resulting implications, three prominent philosophical responses emerge, the first being hard determinism. Hard determinism views a deterministic universe — where every effect results from a pre-existing cause — as being incompatible with free will. To the hard determinist, the laws of physics serve as catalysts for the unambiguous cause-and-effect relationships that make up our world, implying that only one future can result from an initial set of circumstances. A rock thrown up into the air must come down, unless a physical force prevents it from doing so. The future of a system could even be theoretically calculated if all the starting conditions and the mathematics underlying the succeeding interactions are known. With the tossed rock, its trajectory could be precisely mapped by considering the velocity at which it initially was thrown, the effect of gravity on its acceleration, and other more subtle factors, such as the interaction between the air and the material composition of the rock. In practice, even for an observation as deceptively simple as this, it is impossible to know all the pertinent factors and their relationships; as a result, scientists must settle for an imperfect and incomplete list of parameters. And, for a scientist, this may not pose a serious obstruction to their goals. The job of the philosopher, on the other hand, is to describe the fundamental nature of things; the necessary extrapolation from imperfect observation to philosophical ideology inevitably introduces uncertainty.
Nevertheless, despite an inability to map the world with perfect fidelity, cause and effect does appear to be a fundamental principle of nature. For instance, manipulating a variable in a system often leads to an expected change in result. Throwing a rock with a greater initial velocity leads to a longer flight time — a change in cause leading to a change in effect. If the entire universe similarly conforms to cause and effect, then the human mind is no exception. Even the deeply personal process of intentional thought relies on the firing of certain cells in the brain, a physical response to an influx of charged ions, such as calcium and sodium. On what evidence, then, can one claim to be the source of an action, or even a thought? A hard determinist does not find any affirmative answer to the preceding question compelling. Further, they claim, it is inappropriate to exempt the mind from a universal law of cause and effect, and thus, most reasonably concluded, free will is only a tantalizing illusion, the conscious mind a passive observer to the restraining forces of the universe.
Libertarianism is a second philosophical response that similarly views causal determinism as incompatible with free will. Instead of accepting causal determinism at the expense of free will, however, libertarians do the opposite: they reject causal determinism and accept free will. An alluring argument for libertarianism is that free will subjectively feels real; surely, from a human perspective — despite all the difficulties associated with introspection (the observation of one’s own mind) — surely we can at least be confident that we control our thoughts and actions to some extent. For some, the preceding sentence sums up the intuitive experience of free will and sufficiently justifies its existence, while others, including adherents to hard determinism, will be unsatisfied with such a heavy reliance on subjectivity. To provide a more objective explanation aligned with the standard requirements of philosophical scrutiny, another libertarian approach is to focus on a common specification of free will, namely the principle of alternative possibilities, whereby the future is not inevitable and, rather, multiple realities can possibly result from a starting condition. A crude rock toss may appear to manifest in a predictable way — but only from a lack of precision. Zooming in, down to the scale of the smallest subatomic particles, and suddenly the immediate behavior of particles is anything but predictable; rather, it is random, converging to a probability distribution only after the accumulation of many singular instances of behavior. Subatomic particles, fundamental yet random, provide a counterexample to the notion of strict cause and effect that a deterministic universe implies. Perhaps then, free will can propagate via some non-deterministic process as well. Notably, the randomness in subatomic particles stems from a source many levels of scale below an agent, a term implicating a conscious mind, generally that of a human. Only through the interaction of countless random particles does a mind come to fruition, and by what mechanism an agent could exert control over this randomness, or another similarly random process, to perform a non-deterministic act is unclear.
In an attempt to implicate a human agent, some libertarians posit the existence of an unexplainable and immaterial soul removed from the constraints of the laws of physics, from which the will propagates. In response, a couple brief historical examples are insightful. The Mayans believed the movement of the sun was under the influence of gods, and that sacrificial rituals were necessary to ensure its safe passage. According to the ancient Greeks, Zeus wielded lightning bolts as weapons and established dominance by throwing them across the sky. Today, these explanations of natural phenomena only provoke interest as metaphors outside the realm of scientific inquiry; but, in their respective time periods, the Mayans and Greeks viewed them as literal facts. A diligent philosopher should heed the precedent set by their mistaken predecessors, and be wary before proposing an explanation that implicates something as an end itself, not requiring, or even allowing, further explanation. Still, for many libertarians, the deterministic inference that the mind must entirely obey the demands of cause and effect, particularly in light of randomness in the quantum realm, does not supersede the subjective nature of free will, and how it feels undeniably real.
Weighing a deterministic universe against the subjectively real feeling of free will, a third philosophical camp attempts to reconcile the two apparently contradictory ideas. Appropriately, members of this group are labeled compatibilists. Compatibilism takes many different forms, but the most prominent modern view begins by scrutinizing the initial definition of free will: what is meant by requiring that “one chooses their own actions”? A compatibilist accepts causal determinism and thus cannot use any theory of alternative possibilities to justify a free choice. Instead, a compatibilist grants free will in the following sense: a human agent can observe their surroundings, assess the initial condition in which they find themselves, imagine various, diverging future possibilities stemming from that initial condition, and then decide towards which future possibility to act. This cognitive process, albeit determined, is itself free will. Incompatibilists, such as libertarians and hard determinists, claim that the inevitability of the decision excludes it from being considered “free.” A modern compatibilist likely agrees with this claim, but does not view the “free” aspect of free will as all that important; in fact, the term “free will” may be an inappropriate one to describe the controversial concept of discussion. If the question of free will is a game, then compatibilists seek to question the rules, to redefine what should constitute free will.
From the compatibilist perspective, the importance of a decision often lies in the utility of response behaviors. Over millions of years, humans have continuously evolved more efficient and intricate ways to deal with threats in their environments. Prodding a hippopotamus is likely to produce only one unappealing outcome for the prodder, while the same behavior directed towards a human can elicit many different outcomes: the person could respond aggressively like the hippopotamus, but they could also choose to walk away, or even verbally question the motives of the other. This abundance of response behaviors underlies the actual importance of free will to a compatibilist, regardless of whether or not the behavior is physically determined. Compatibilism seeks a compromise, adhering to the hard determinist’s view of a deterministic universe, while at the same time emphasizing the importance of the intuitive feeling of free will recognized by libertarians, melding the two viewpoints into a cohesive framework of the human experience.
From these three philosophical viewpoints, the question of moral responsibility naturally emerges. Free will rests on a shaky foundation, its existence elusive even in a scientifically impressive era; if we assume that free will is no more than an enticing illusion, then how can we hold individuals accountable for actions over which they exert no control?
– Written by Matthew Eitzman