And we will see that the departure from strict causality needed to negate determinism is very slight compared to the miraculous ideas associated with the "causa sui" (self-caused cause) of the ancients, which most modern thinkers find unintelligible (with the exception of many theists, who accept the idea of miracles).

Few commentators note that Hume's view that we all have an unshakeable natural belief in causality, despite the impossibility of a logical proof of causality or a successful attack on his logical skepticism.

Bertrand Russell said "The law of causation, according to which later events can theoretically be predicted by means of earlier events, has often been held to be a priori, a necessity of thought, a category without which science would not be possible." (Russell, External World p.179)

Now the assumption of deterministic causation underlies most successful scientific theories, with the critical exception of quantum mechanics. Some major objections to the causal determinism implied by Newtonian laws of motion are the claim that

• The complete predictability of future events is possible in principle (Laplace's Demon)
• There is only one possible future, even if it is unpredictable
• The laws of motion are time reversible
• Given enough time, all the positions and motions will recur

The core idea of indeterminism is an event without a cause. Quantum mechanics does not go so far as to say that events have absolutely no causal connection with the events (the distribution of matter and motions) of the immediate past). What it does do is introduce events with a statistical cause. And quantum mechanics makes extremely accurate predictions of the probabilities for the different random outcomes.

So we can have an adequate or statistical causality without strict determinism, which otherwise implies complete predictability of events and only one possible future.

An example of an event that is not strictly caused is one that depends on chance, like the flip of a coin. If the outcome is only probable, not certain, then the event can be said to have been caused by the coin flip, but the head or tails result itself was not predictable. So this causality, which recognizes prior events as causes, is undetermined and the result of chance alone. It is statistical causality, actually the only kind of causality we have.

We call this "soft" causality. Events are caused by prior (uncaused) events, but are not completely determined by prior events in the causal chain back to a primal first cause. That Aristotelian chain (ἄλυσις) has been broken by the uncaused cause. Uncaused events start new causal chains. Aristotle himself called these events "new beginnings" or archai (ἀρχαί).

Most events are "adequately determined." No events are pre-determined in the Laplacian or theological senses.

Determinism is critical for the question of free will. Strict determinism implies just one possible future. Chance means that the future is open and unpredictable. Chance allows alternative futures and the question becomes how the one actual present is realized from these potential alternatives.

Even in a world that contains quantum uncertainty, macroscopic objects are determined to an extraordinary degree. Newton's laws of motion are deterministic to the limits of observational error. Our Cogito model of a "Macro Mind" makes it large enough to ignore quantum uncertainty for the purpose of the reasoning will. The neural system is robust enough to insure that mental decisions are reliably transmitted to our limbs.

We call this kind of determinism, limited as it is in extremely small structures, "adequate determinism." The presence of quantum uncertainty leads philosophers to call the world "indeterministic." But indeterminism is seriously misleading when most events are overwhelmingly "adequately determined."

There is no problem imagining that the three traditional mental faculties of reason - perception, conception, and comprehension - are all carried on essentially deterministically in a physical brain where quantum events do not interfere with normal operations.

There is also no problem imagining a role for randomness in the brain in the form of quantum level and thermal noise. Noise can introduce random errors into stored memories. Noise could create random associations of ideas during memory recall and the important process of memory consolidation.

Many philosophers and scientists have suggested that microscopic quantum fluctuations are amplified to the macroscopic level. But they need not be the direct cause of human actions.

Our Macro Mind needs the Micro Mind for the free action items and thoughts in an Agenda of alternative possibilities to be de-liberated by the will. The random Micro Mind is the "free" in free will and the source of human creativity. The adequately determined Macro Mind is the "will" in free will that de-liberates, choosing actions for which we can be morally responsible.

Causality must be disambiguated from its close relatives certainty, determinism, necessity, and predictability.

Free will libertarians have imagined exceptions to causality that they call "agent-causality" and "non-causality."

The first agent-causal libertarian was Aristotle, followed by Epicurus, and then Carneades. In more recent times, prominent agent-causalists have been Thomas Reid in the 18th century, and Roderick Chisholm, Richard Taylor, Keith Lehrer, Timothy O'Connor, and Randolph Clarke in the 20th century.

The author of "non-causality" is Carl Ginet. He maintains that no cause is needed for human decisions. We can summarize the positions of these libertarians, all of which admit some indeterminism, in a diagram, part of the taxonomy of all free will positions.