The physical location of randomness in the brain and the timing of chance mental events relative to the decision of the determined will are the two most critical problems for any model of libertarian free will.

Philosophers and scientists have imagined a number of fanciful randomness generating mechanisms.

Some thinkers have stressed the importance of locating randomness properly (physically and temporally), notably Robert Kane, Laura Waddell Ekstrom, and Alfred Mele.

Kane is wary of quantum processes amplified to affect the macroscopic brain. He says about them...

"We do not know if something similar goes on in the brain of cortically developed creatures like ourselves, but I suspect it must if libertarian theories are to succeed. The main problem is the one addressed by Eccles of locating the master switch and the mechanisms of amplification. We have no substantial empirical evidence on these matters (especially regarding the master switch), merely speculation, and libertarian theories may fail dismally at this juncture. But there is much to be learned yet about the brain; and research exists...suggesting that master switch plus amplifier processes play more roles in the functioning of organisms than was previously supposed.

[L]et us now suppose that there are neurons in the brain "critically poised" in Eccles' sense, whose probability of firing within a small interval of time is .5. For practical choice, these ordered combinations of firings and non-firings of critically poised neurons would correspond to places on a spinning wheel, most of which would give rise to chance selected considerations, opening doors to consciousness of possibly relevant memories, triggering associations of ideas and/or images, focussing attention in various ways, etc. Some combinations of firings and non-firings might draw a blank. But the wheel would keep spinning until it hit something worth considering, so long as the practical reasoner or creative thinker were in a receptive, yet reflective, state of mind. Then the relevance of the consideration to deliberation would have to be assessed and the consideration either accepted or rejected. (Free Will and Values, 1985, p. 168-9)

Kane imagines a spinning wheel on which there are equiprobable segments each containing a "bubble" representing a quantum probability wave. When it is near the top of the enclosing tube, the choice is made according to duty, when the bubble moves down, the choice is made from self-interest. The critical point is that Kane includes randomness in the choice, which is unacceptable, since it makes our choices random.

"One might think of this as a picture of an air bubble in a glass tube filled with a liquid, with the lines A and B marked on the outside of the glass as on an ordinary carpenter's level. But this description is merely an aid to the imagination. We are going to give the bubble some extraordinary properties. The bubble may represent either the desire to choose to act from duty (out of equal respect) or the effort made to realize this desire in choice. The respective desire and effort are conceptually related because the desire is defined as the disposition to make the effort; and the intensity of the desire is measured by the intensity of the effort. The lines A and B in the figure represent choice thresholds. If the bubble passes above the line A, the choice is made to act from duty; if it passes below B, the choice is made to act on self interested motives. When the bubble is between the lines, as in the figure, no choice has yet been made.' A downward pull of gravity in the figure may be thought to represent the natural pull of one's self interested motives, which must be counteracted by an effort to resist temptation. [Kane mixes his metaphors of quantum probability waves and matter responding to gravity.]

There is an ambiguity, essential to our problem, about what it means to say that the bubble "passes above" the line A, or "below" the line B. If the bubble passes above A, or below B, then the choice is made to act from duty, or from self interest, respectively. But does this mean that the bubble must be wholly, or only partly, above A, or below B? It is here that we give the bubble some extraordinary properties. We imagine that the bubble represents a probability space, so that, when it is partly above A, there is a corresponding probability, but not certainty that the choice is made to act from duty, and when it is partly below B there is a corresponding probability, but not certainty, that the choice is made to act from self interest. When the bubble is wholly above A (or below B), it is certain that the choice is made to act from duty or self interest). We then imagine a point particle in the probability space (the bubble) that moves around randomly, while always remaining within the space. That is, it has an equal probability of appearing in any one of a number of equal sized regions in the space. If part of the bubble is above the line A for a certain time and the point particle is in regions all of which are wholly above the line for the same length of time, then the choice is made to act from duty (and similarly for line B). (Free Will and Values, 1985, p. 144-5)

In Kane's most recent comment on indeterminism in his free will model, he correctly identifies "noise" as the proper source.

"As it happens, on my libertarian account of free will, one does not need large-scale indeterminism in the brain, in the form, say, of macro-level wave function collapses (in the manner of the Penrose/Hameroff view mentioned by Vargas). Minute indeterminacies in the timings of firings of indeterminism neurons would suffice, because the indeterminism in my view plays only an interfering role, in the form of background noise. Indeterminism does not have to "do the deed" on its own, so to speak. One does not need a downpour of indeterminism in the brain, or a thunderclap, to get free will. Just a sprinkle will do." (Four Views on Free Will, Fischer et al., p.183)

Laura Waddell Ekstrom pays a lot of attention to where exactly the indeterminism is located in the process. But like Kane, she thinks she needs to keep some indeterminism in the last, decision phase, otherwise a duplicate agent would make the same choice given the same alternative possibilities (which is exactly what a determined will, acting consistently with its character and values, should do!). She says:

The First Problem: Indeterminism Where?

"Libertarians, then, share the problem of providing a positive thesis concerning the metaphysical conditions enabling free will. Without a solution to the where's the indeterminism? problem, libertarian accounts of the nature of free will cannot get off the ground. This problem is the central, most significant difficulty for the endeavor of presenting a plausible incompatibilist account of the nature of free action: locating the requisite indeterminism in the causal history of the act, together with explaining why this precise location is appropriate and important." (Free Will: A Philosophical Study, 2000, p.85)

Any incompatibilist model of freedom is going to have to locate the event-causal indeterminism somewhere in the history of the free act, and the specified place — between the considerations and the decisive formation of preference — seems to me the most reasonable place to locate it. One might, instead, locate the indeterminism prior to some of the considerations that occur to the agent during the deliberative process, so that what is undetermined is which (and perhaps at what points during the process) particular considerations come into the agent's mind. But if this were the only place specified for required indeterminism, then an act might be the purely causally deterministic outcome of the considerations that happen to occur to the agent and yet, on the proposal, count as free. Such an account is too weak to ground agent freedom and deep responsibility, since, given the occurrence of the particular considerations in any case, one particular act follows of physical necessity, as the completely deterministic unfolding of previous events. (p.120)

Consider an agent whose act is, in such a sense, "libertarian free." Now a duplicate agent in exactly similar circumstances governed by the same natural laws and subject to the same occurrence of considerations at the same points in the deliberative process will form exactly the same judgment concerning the best thing to do and will act accordingly. But then, given the consideration pattern that occurs (but might not have), there is no "wiggle room" for the agent in forming an evaluative judgment—it simply falls out, of necessity, from the consideration pattern. Hence such an account does not leave sufficient room for free agency. (p.121)

Where causal indeterminism is best located, instead, is after the considerations (which in the usual case have been determined to occur by previous events, such as how much rest one has had, what one has recently eaten, with whom one has recently spoken, what one has read) yet prior to the decisive formation of preference, such that given the exact consideration pattern, the agent may decide to prefer a and may decide to prefer otherwise. The considerations themselves are indeterministic causes of the preference.

Alfred Mele in his 1995 book Autonomous Agents and again in his 2006 Free Will and Luck, proposed a "Modest Libertarianism" for consideration by libertarians. He himself did not endorse the idea. But he made clear, following Daniel Dennett's "Valerian" model in Brainstorms, 1978, that the indeterminism should come early in the overall process. He even describes the latter - decision - part of the process as compatibilist (effectively determinist).

Mele sees, unlike Kane and Ekstrom, that the requirements for the will must be adequate determinism.

"These observations indicate that it might be worth exploring the possibility of combining a compatibilist conception of the later parts of a process issuing in full blown, deliberative, intentional action with an incompatibilist conception of the earlier parts. For example, it might be possible to gain "ultimate control" while preserving a considerable measure of nonultimate agential control by treating the process from proximal decisive better judgment through overt action in a compatibilist wav and finding a theoretically useful place for indeterminacy in processes leading to proximal decisive better judgments. (p.212)

Is this Fischer's semi-compatibilism?

Recall that compatibilism does not include a commitment to determinism. The thesis is that determinism does not preclude autonomy. Treating the process from proximal decisive better judgment through overt action in a compatibilist way does not require treating it in a determinist way. Compatibilists may, in principle be willing to accept an account of causation that accommodates both deterministic and probabilistic instances, and they are not committed to holding that probabilistic causation in the process just mentioned precludes the freedom of its product. In the same vein, advocates of autonomy who seek a "theoretical) useful place" for indeterminism in the springs of action need not insist that indeterminism does not appear at other places, as well, in internal processes issuing in autonomous action. Their claim on that matter may merely be that indeterminism at these other junctures is of no use to them. (p.213)

External indeterminism, as I have already explained, does not give libertarians what they want. That leaves internal indeterminism. Assume, for the sake of argument, that human beings sometimes act autonomously, that acting autonomously requires "ultimate control," and that the latter requires internal indeterminism. Then, with a view to combining ultimate control with robust nonultimate control, we can ask what location(s) for internal indeterminism would do us the most good. (p.213)

The only reasonable model for an indeterministic contribution is ever-present noise throughout the neural circuitry. We call it the Micro Mind.

Quantum (and even some thermal) noise in the neurons is all we need to supply random unpredictable alternative possibilities.

And indeterminism is NOT involved in the de-liberating Will. We call it the Macro Mind.

The major difference between Micro and Macro is how they process noise in the brain circuits. The first accepts it, the second suppresses it.

Our "adequately determined" Mind can overcome the noise whenever it needs to make a determination on thought or action.

Will neuroscientists ever find information structures in the brain to generate our random agenda, structures small enough to be susceptible to microscopic quantum phenomena?

Some fanciful mechanisms include a random number generator like those in computer programs. Others imagine a microscopic event like the nuclear decay in Schrödinger's diabolical thought experiment with a cat, plus the amplifier circuitry needed to magnify the event to the macroscopic level.

But nothing physically localized is likely to be found. The randomness of the Micro Mind is simply the result of ever-present noise, both thermal and quantum noise, that is inherent in any information storage and communication system.

Constant, ever-present noise removes an important technical objection. When and where and how would the random event occur?, said critics of the Epicurean swerve of the atoms. The Cogito model randomly generates contextually appropriate alternative possibilities at all times.

The Cogito model is not a mechanism. It is a process.

Quantum uncertainty adds a "causa sui," an uncaused or self-caused cause, in the causal chain. But it need not directly determine the decision of the macroscopic will or the fully determined resulting action which is consistent with character and values.

Some argue that brain structures are too large to be affected at all by quantum events. But there is little doubt that the brain has evolved to the point where it can access quantum phenomena. The evolutionary advantage for the mind is freedom and creativity. Biophysics tells us the eye can detect a single quantum of light (photon), and the nose can smell a single molecule.

If the Micro Mind is a random generator of frequently outlandish and absurd possibilities, the complementary Macro Mind is a macroscopic structure so large that quantum effects are negligible. It is the critical apparatus that makes decisions based on our character and values.

Information about our character and values is probably stored in the same noise-susceptible neural circuits of our brain, in our memory, so Macro Mind and Micro Mind are not necessarily in different locations in the brain. Instead, they are probably the consequence of different information processing methods. The Macro Mind must suppress the noise when it makes an adequately determined decision.

The Macro Mind has very likely evolved to add enough redundancy, perhaps even error detection and correction, to reduce the noise to levels required for an adequate determinism. Our decisions are then in principle predictable, given knowledge of all our past actions and given the randomly generated possibilities in the instant before decision. However, only we know the contents of our minds, and they exist only within our minds. Thus we can feel fully responsible for our choices, morally and legally.

The Cogito model accounts not just for freedom but for creativity, original thoughts and ideas never before expressed. Unique and new information comes into the world with each new thought and action.

Biologists will note that the Micro Mind corresponds to random variation in the gene pool (often the direct result of quantum accidents). The Macro Mind corresponds to natural selection by highly determined organisms. See the biology chapter for other examples of random generation followed by adequately determined selection, like the immune system and protein/enzyme factories. Karl Popper may have been the first to point this out.

Psychologists will see the resemblance of Micro Mind and Macro Mind to the Freudian id and super-ego (das Ess und das Über-ich).