Determinism is the philosophical idea that every event or state of affairs, including every human decision and action, is the inevitable and necessary consequence of antecedent states of affairs.

Determinism is a modern name (nineteenth-century) for Democritus' ancient idea that causal laws control the motion of atoms, and that everything - including human minds - consists merely of atoms in a void.

As Democritus' mentor and fellow materialist Leucippus put it, an absolute necessity leaves no room in the cosmos for chance.

"Nothing occurs at random, but everything for a reason and by necessity." ¹

οὐδὲν χρῆμα μάτην γίνεται, ἀλλὰ πάντα ἐκ λόγου τε καὶ ὑπ’ ἀνάγκης

Determinism, especially the variation of "soft" determinism (cf. William James) or compatibilism, is supported as a theory of free will by a majority of philosophers, each with special vested interests in one or more of the many determinisms.

Compatibilism is a form of determinism that argues man is free as long as his own will is one of the steps in the causal chain, even if his choices are completely predetermined for physical reasons or preordained by God.

And Fatalism is a special form of determinism where every event in the future is fated to happen. Fatalism does not normally require that any causal laws or higher powers are involved. Que sera, sera.

The core idea of determinism is closely related to the idea of causality. But we can have causality without determinism, especially the "soft" causality that follows an "uncaused" event (a causa sui) that is not predictable from prior events.

Aristotle called such events archai (ἀρχαί) - starting points or "fresh starts" in new causal chains which break the bonds of determinism.

Despite David Hume's critical attack on the necessity of causes, many philosophers embrace causality and determinism strongly. Some even connect it to the very possibility of logic and reason. And Hume himself believed strongly, if inconsistently, in necessity. " 'tis impossible to admit any medium betwixt chance and necessity," he said.

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)

The idea of indeterminism appears to threaten causality and the basic idea of causal law. But it does not.

Indeterminism for some is simply an occasional event without a cause. We can have an adequate causality without strict determinism. Strict determinism means complete predictability of events and only one possible future. Adequate determinism provides statistical predictability, which in normal situations for physical objects approaches statistical certainty.

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.

We call this "soft" causality. Events are caused by prior (uncaused) events, but not determined by events earlier in the causal chain, which has been broken by the uncaused cause.

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

The departure required from strict determinism is very slight compared to the miraculous ideas associated with the "causa sui" (self-caused cause) of the ancients.

Even in a world that contains quantum uncertainty, macroscopic objects are determined to an extraordinary degree. Newton's laws of motion are deterministic enough to send men to the moon and back. Our Cogito Model of the Macro Mind is 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 determinism, only ineffective for extremely small structures, "adequate determinism." Determinism is adequate enough for us to predict eclipses for the next thousand years or more with extraordinary precision.

Belief in strict determinism, in the face of physical evidence for indeterminism, is only tenable today for dogmatic philosophy. We survey ten modern dogmas of determinism.

Phillipa Foot argued that because our actions are determined by our motives, our character and values, our feelings and desires, in no way leads to the conclusion that they are predetermined from the beginning of the universe.

The presence of quantum uncertainty leads some philosophers to call the world indetermined. But indeterminism is somewhat misleading, with strong negative connotations, when most events are overwhelmingly "adequately determined." Nevertheless, speaking logically, if a single event is undetermined, then indeterminism is true, and determinism false. ¹

There is no problem imagining that the three traditional mental faculties of reason - perception, conception, and comprehension - are all carried on 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 noise. Noise can introduce random errors into stored memories. Noise could create random associations of ideas during memory recall. This randomness may be driven by microscopic fluctuations that are amplified to the macroscopic level.

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.

Determinism must be disambiguated from its close relatives causality, certainty, necessity, and predictability.

The term (sic) determinism is first attested in the late fourteenth century, "to come to an end," also "to settle, decide," from O.Fr. determiner (12c.), from L. determinare "set limits to," from de- "off" + terminare "to mark the end or boundary," from terminus "end, limit."

The sense of "coming to a firm decision" (to do something) is from 1450.

Determination as a "quality of being resolute" dates from 1822.

Before the nineteenth century determinists were called Necessarians. William Belsham contrasted them (favorably) with the incoherent Libertarians in 1789, the first use of Libertarian.

Determinism appears in 1846 in Sir William Hamilton's edition of Thomas Reid's works as a note on p.87.

There are two schemes of Necessity - the Necessitation by efficient - the Necessitation by final causes. The former is brute or blind Fate; the latter rational Determinism.

At about the same time, it is used by theologians to describe lack of free will.

In 1855, William Thomson (later Lord Kelvin) wrote,

The theory of Determinism, in which the will is determined or swayed to a particular course by external inducements and forced habits, so that the consciousness of freedom rests chiefly upon an oblivion of the antecedents of our choice.

Ernst Cassirer claimed (mistakenly?) that Determinism in the philosophical sense of a "doctrine that everything that happens is determined by a necessary chain of causation." dates from 1876.

Note that ancient philosophers worried about this causal chain (ἄλυσις), but those philosophers who allowed the existence of chance, (Aristotle, Epicurus, Lucretius, and Alexander of Aphrodisias), denied such a causal chain, while maintaining that human decisions were caused by neither chance nor necessity but by a tertium quid - our autonomous human agency.

The adjective determinist appeared first in the Contemporary Review of October 1874 - "The objections of our modern Determinists." In the Contemporary Review of March 1885 R. H. Hutton described "The necessarian or determinist theory of human action."