Benjamin Libet's experiments and measurements of the time before a subject is aware of self-initiated actions have had a enormous, mostly negative, impact on the case for human free will, despite Libet's view that his work does nothing to deny human freedom. The original discovery that an electrical potential (of just a few microvolts - μV) is visible in the brain long before the subject flexes a finger was made by Kornhuber and Deecke (1964). They called it a "Bereitschaftspotential" or readiness potential. The neurobiologist John Eccles speculated that the subject must become conscious of the intention to act before the onset of this readiness potential. Benjamin Libet decided to test Eccles's idea.
We don't know what specific unconscious mental processes the RP might represent....The position of conscious will in the time line suggests perhaps that the experience of will is a link in a causal chain leading to action, but in fact it might not even be that. It might just be a loose end — one of those things, like the action, that is caused by prior brain and mental events.Does the compass steer the ship? In some sense, you could say that it does, because the pilot makes reference to the compass in determining whether adjustments should be made to the ship's course. If it looks as though the ship is headed west into the rocky shore, a calamity can be avoided with a turn north into the harbor. But, of course, the compass does not steer the ship in any physical sense. The needle is just gliding around in the compass housing, doing no actual steering at all. It is thus tempting to relegate the little magnetic pointer to the class of epiphenomena — things that don't really matter in determining where the ship will go. Conscious will is the mind's compass. As we have seen, the experience of consciously willing action occurs as the result of an interpretive system, a course-sensing mechanism that examines the relations between our thoughts and actions and responds with "I willed this" when the two correspond appropriately. This experience thus serves as a kind of compass, alerting the conscious mind when actions occur that are likely to be the result of one's own agency. The experience of will is therefore an indicator, one of those gauges on the control panel to which we refer as we steer. Like a compass reading, the feeling of doing tells us something about the operation of the ship. But also like a compass reading, this information must be understood as a conscious experience, a candidate for the dreaded "epiphenomenon" label. Bernard Baars says there are two important time scales of consciousness
Sensory events occurring within a tenth of a second merge into a single conscious sensory experience, suggesting a 100-millisecond scale. But working memory, the domain in which we talk to ourselves or use our visual imagination, stretches out over roughly 10-second steps. The tenth-of-a-second level is automatic, while the 10-second level is shaped by conscious plans and goals.The kinds of deliberative and evaluative processes that are important for free will involve longer time periods than those studied by Benjamin Libet. Note also that the abrupt and rapid decisions to flex a finger measured by Libet bear little resemblance to the kinds of two-stage deliberate decisions for which we can first freely generate alternative possibilities for action, then evaluate which is the best of these possibilities in the light of our reasons, motives, and desires - first "free," then "will."
We should also distinguish between deliberations about what choice of action to adopt (including preplanning of when to act on such a choice), and the final intention to actually "act now." One may, after all, deliberate all day about a choice but never act...Libet also wrote extensively on the use of his experiments to claim that mental processes were as deterministic as those in physics. He proposed the term "nondeterminism."
Determinism and Free Will
There remains a deeper question about free will that the foregoing considerations have not addressed. What we have achieved experimentally is some knowledge of how free will may operate. But we have not answered the question of (i) whether our consciously willed acts are fully determined by natural laws that govern the activities of nerve cells in the brain, or (2) whether freely voluntary acts, and the conscious decisions to perform them, can proceed to some degree independently of natural determinism. The first of these options would make free will illusory. The conscious feeling of exerting one's will would then be regarded as an epiphenomenon, simply a by-product of the brain's activities with no causal powers of its own. The view that free will is illusory is elaborated at some length by Wegner (2002). There are, of course, other contributors to this view, like the Churchlands (1999) and Dennett (1984). Wegner proposes a "theory of apparent mental causation" that states: "People experience conscious will when they interpret their own thought as the cause of their action" (p. 64 in his book). That is, the experience of conscious will is "quite independent of any actual causal connection between their thoughts and their actions." It is, of course, legitimate to propose this arrangement as a theory for free will within a deterministic view. But there is no crucial evidence that proves its validity. No experimental test has even been proposed in which this theory could be falsified. Without any possibility of falsification, one can propose anything without any fear of being contradicted (as Karl Popper explained). First, free choices or acts are not predictable, even if they are viewed as completely determined. The "uncertainty principle" of Heisenberg precludes our having a complete knowledge of the underlying molecular activities. Quantum mechanics forces us to deal with probabilities, rather than with certainties of events. And, in chaos theory, a random event may shift the behavior of a whole system in a way that was not predictable. However, even if events are not predictable in practice, that does not exclude the possibility that they are following natural laws and therefore determined. Let us rephrase our basic question as follows: Must we accept determinism? Is nondeterminism a viable option? We should recognize that both of these alternative views (natural law determinism versus nondeterminism) are unproven theories, in other words, unproven in relation to the existence of free will. Determinism (adherence to natural law) has, on the whole, worked well for the physical observable world. That has led many scientists and philosophers to regard any deviation from such determinism as absurd, witless, and unworthy of consideration. But natural laws were derived from observations of physical objects, not from subjective mental phenomena. The latter cannot be directly observed; they are inner experiences of the individual who has them. There has been no evidence, or even a proposed experimental test design, that definitively or convincingly demonstrates the validity of natural law determinism as the mediator or instrument of free choice or free will. There is an unexplained gap between the category of physical phenomena, and the category of subjective phenomena. Researchers as far back as Leibniz have pointed out that if you looked into the brain with a full knowledge of its physical makeup and nerve cell activities, you would see nothing that described subjective experience. You would only see cellular structures, their interconnections, and the production of nerve impulses and other electrophysiological events, as well as metabolic chemical changes. The foundation of our own experimental studies of the physiology of conscious experience (beginning in the late 1950s) was that externally observable brain processes and the related reportable subjective introspective experiences must be studied simultaneously, as independent categories, to understand their relationship. The assumption that a deterministic nature of the physically observable world can account for subjective conscious functions and events is a speculative belief, not a scientifically proven proposition. (Of course, modern physics teaches us that even physical events may not be determined or predictable. Even so, these physical events are following the natural laws at the macro level. However, that does not exclude the possibility that physical events are susceptible to an external "mental force" at the micro level, in a way that would not be observable or detectable). Nondeterminism—which is the view that conscious will may, at times, exert effects not in accord with known physical laws— is of course also a nonproven speculative belief. The view that conscious will can affect brain function in violation of known physical laws takes two forms. One view is that the violations are not detectable, because the actions of the mind may be at a level below that of the uncertainty allowed by quantum mechanics. (Whether this last proviso can in fact be tenable is a matter yet to be resolved.) This view would thus allow for a nondeterministic free will to occur without a perceptible violation of physical laws. A second view holds that violations of known physical laws are large enough to be detectable, at least in principle. But it can be argued that detectability in actual practice may be impossible. That difficulty for detection would be especially true if the conscious will is able to exert its influence by minimal actions at relatively few nerve elements, if these actions could serve as triggers for amplified nerve cell patterns of activity in the brain. In any case, we do not have a scientific answer to the question of which theory (determinism or nondeterminism) correctly describes the nature of free will. However, it is important to recognize an almost universal experience: that we can act in certain situations with a free, independent choice and control of whether to act. The simplest example of this is the one we employed in our experimental study—the conscious will to flex the wrist in a freely capricious manner. This provides a kind of prima facie evidence that conscious mental processes can causally control some brain processes (Libet, 1993, 1994). Of course, the nature of this experience must be qualified. Our own experimental findings showed that conscious free will does not initiate the final "act now" process; the initiation of it occurs unconsciously. But, as discussed previously, conscious will certainly has the potentiality to control the progress and outcome of the volitional process. Thus, the experience of independent choice and of control (of whether and when to act) does have a potentially solid validity as not being an illusion. The cerebral nature of considering choices of action, by conscious deliberation and preplanning before any "act now" process, is yet to be elucidated. How does this experience dovetail with the view of an experimental scientist? It appears to create more difficulty for a determinist than for a nondeterminist option. The phenomenal fact is that most of us feel that we do have a kind of free will, at least for some of our actions, within certain limits that may be imposed by our brain's status and by our environment. Our intuitive feelings about the phenomenon of free will form a fundamental basis for our views about human nature. Great care should be taken not to believe allegedly scientific conclusions about our nature that depend on hidden ad hoc assumptions. A theory that simply interprets the phenomenon of free will as illusory and denies the validity of this phenomenal fact is less attractive than a theory that accepts or accommodates the phenomenal fact. Given that the issue is so fundamentally important to our view of who we are, a claim that our free will is illusory should be based on fairly direct evidence. Theories are supposed to explain observations, not do away with them or distort them, unless there is powerful evidence to justify that. Such evidence is not available, and determinists have not proposed any potential experimental design to test their theory. The elaborate proposals that free will is illusory, like that of Wegner (2002), fall into this category. It is foolish to give up our view of ourselves as having some freedom of action and of not being predetermined robots on the basis of an unproved theory of determinism. My conclusion about free will, one genuinely free in the nondetermined sense, is that its existence is at least as good, if not a better, scientific option than is its denial by natural law determinist theory. Given the speculative nature of both determinist and nondeterminist theories, why not adopt the view that we do have free will (until some real contradictory evidence appears, if it ever does)? Such a view would at least allow us to proceed in a way that accepts and accommodates our own deep feeling that we do have free will. We would not need to view ourselves as machines that act in a manner completely controlled by known physical laws. Such a permissive option has also been recently advocated by the neurobiologist Roger Sperry (see Doty, 1998). I close, then, with a quotation from the great novelist Isaac Bashevis Singer. Singer stated his strong belief in our having free will. In an interview (Singer, 1968), he volunteered that, "The greatest gift which humanity has received is free choice. It is true that we are limited in our use of free choice. But the little free choice we have is such a great gift and is potentially worth so much that for this itself life is worthwhile living."