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 had 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.

Libet's clock. Click to enlarge

Libet's 1983 experiments measured the time when the subject became consciously aware of the decision to move the finger. Libet created a dot on the screen of an oscilloscope circulating like the hand of a clock. The subject was asked to note the position of the moving dot when he/she was aware of the conscious decision to move a finger or wrist.

Libet's results were eagerly adopted by the deniers of free will to indicate that the mind had been made up unconsciously, long before any awareness of "conscious will."

Psychologist Daniel Wegner thinks that conscious will may be just an epiphenomenon, something that is caused by brain events, not the cause of such events. As he put it in his 2002 book The Illusion of Conscious Will,

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.

(The Illusion of Conscious Will, MIT Press, p.55)

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.

(The Illusion of Conscious Will, MIT Press, p.317)

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.

(In the Theater of Consciousness, p.48)

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 can correlate the beginnings of the readiness potential (350ms before Libet's conscious will time "W" appears) with the early stage of the two-stage model, when alternative possibilities are being generated, in part at random. The early stage may be delegated to the subconscious, which is capable of considering multiple alternatives (William James' "blooming, buzzing confusion") that would congest the single stream of consciousness.

Alfred Mele has criticized the interpretation of the Libet results on two grounds. First, the mere appearance of the RP a half-second or more before the action in no way makes the RP the cause of the action. It may simply mark the beginning of forming an intention to act. In the two-stage model, it is the considering of possible options.

Libet himself argued that there is enough time after the W moment (a window of opportunity) to veto the action, but Mele's second criticism points out that such examples of "free won't" would not be captured in Libet experiments, because the recording device is triggered by the action (typically flicking the wrist) itself.

Thus, although all Libet experiments ended with the wrist flicking, we are not justified in assuming that the rise of the RP (well before the moment of conscious will) is a cause of the wrist flicking. Libet knew that there were very likely other times when the RP rose, but which did not lead to a flick of the wrist.

Thinkers (e.g., Daniel Wegner, Patrick Haggard) who claim that the Libet experiments prove that our conscious will and subsequent actions are caused by prior neural activity - the popular view that "my neurons made me do it" - are simply wrong.

Libet's experiments clearly show a temporal sequence in the decision process, which we argue shows a time in the early stage where indeterminism is operating to generate alternative possibilities, followed by a second stage where the evaluation and decision process is adequately (statistically) determined (e.g., by the agent's reasons and motives).

In his last book, Mind Time: The Temporal Factor in Consciousness, Libet described a process that is very much our two-stage_model.

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...

These remarks by Libet may have inspired Stephen Kosslyn's idea for a two-stage model in his foreword to Mind Time

However, conscious will definitely can control whether the act takes place. We may view the unconscious initiatives for voluntary actions as "burbling up" unconsciously in the brain. The conscious will then selects which of these initiatives may go forward to an action, or which ones to veto and abort so no act occurs.

(Mind Time, pp.148-149)

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."

(Mind Time, pp.151-156)

1. Libet is right to focus on consciousness when theorizing about free will: In order to employ free will, one must evaluate information in working memory. Such information includes the alternative choices, the rationales for each, and the anticipated consequences of making each choice (although not all this information must be in working memory at the same time). If an external force coerces us, or we are operating on "automatic pilot," we are not exercising free will.

2. The rationales and anticipated consequences — and even, depending on the situation, the alternative courses of action — are not simply "looked up" in memory, having been stashed away like notes in a file after previous encounters.

Here Kosslyn considers a first stage of free creation of alternative courses of action

Rather, one constructs rationales and anticipated consequences, as appropriate for the specific situation at hand. This construction process may rely in part on chaotic processes. Such processes are not entirely determined by one's learning history (even as filtered by one's genes). By analogy, consider the path of a raindrop dribbling down a pane of glass. It zigs, it zags, tracing a path best explained with the aid of chaotic principles. The same raindrop, striking precisely the same place on that pane on a warmer day (which would cause the glass to be in a slightly different state) would take a different path. In chaotic systems, very small differences in start state can produce large differences downstream. The pane of glass is like the state of the brain at any instant. Depending on what one was just thinking about, the brain is in a different "start state" (i.e., different information is partially activated, different associations are primed) when one constructs rationales and anticipated consequences — which will affect how one decides. (Note that this idea does not simply move the problem back a step: What one was just thinking itself was in part a result of nondeterministic processes.) Our thoughts, feelings and behavior are not determined; we can have novel insights as well as "second thoughts."

3. Given the choices, rationales, and anticipated consequences, one decides what do on the basis of "what one is" (mentally speaking, to use Strawson's term, which includes one's knowledge, goals, values, and beliefs).

Here Kosslyn considers a second stage of willed decisions that are determined by our goals, values, and beliefs - "what one is"

"What one is" consists in part of information in memory, which plays a key role in the processes that construct the alternatives, rationales, and anticipated consequences. In addition, "what one is" governs how one actually makes the decisions. And making that decision and experiencing the actual consequences in turn modifies "what one is," which then affects both how one constructs alternatives, rationales and anticipated consequences and how one makes decisions in the future. Thus, with time one's decisions construct what one is.

We are not simply accumulators of environmental events, filtered by our genetic make-ups. We bring something novel and unique to each situation — ourselves. Nietzsche (1886, as quoted in Strawson, 1994, p. 15) commented, "The causa sui is the best self-contradiction that has been conceived so far." Maybe not.