Hard determinism (or metaphysical determinism) is a view on free will which holds that determinism is true, and that it is incompatible with free will, and, therefore, that free will does not exist. Although hard determinism generally refers to nomological determinism, it can also be a position taken with respect to other forms of determinism that necessitate the future in its entirety. Hard determinism is contrasted with soft determinism, which is a compatibilist form of determinism, holding that free will may exist despite determinism. It is also contrasted with metaphysical libertarianism, the other major form of incompatibilism which holds that free will exists and determinism is false.
Hard determinism is not taken to refer merely to a determinism on earth, but in all of reality (e.g. involving the effects of light from other galaxies, etc.); not just during a certain deterministic period of time, but for all time. This also means that the relation of necessity will be bi-directional. Just as the initial conditions of the universe presumably determine all future states, so too does the present necessitate the past. In other words, one could not change any one fact without affecting the entire timeline. Because hard determinists often support this eternalist view of time, they do not believe that there are genuine chances or possibilities, only the idea that events are 100% likely.
Unlike “law fundamentalists”, some philosophers are “law pluralists”: they question what it means to have a law of physics. One example is the “Best Standards Analysis”, which says that the laws are only useful ways to summarize all past events, rather than there being metaphysically “pushy’’ entities (this route still brings one into conflict with the idea of free will). Some law pluralists further believe there are simply no laws of physics. The mathematical universe hypothesis suggests that there are other universes in which the laws of physics and fundamental constants are different. Andreas Albrecht of Imperial College in London called it a "provocative" solution to one of the central problems facing physics. Although he "wouldn't dare" go so far as to say he believes it, he noted that "it's actually quite difficult to construct a theory where everything we see is all there is".
The feasibility of testing determinism is always challenged by what we know, or think we can know, about the idea of a final, all encompassing, theory of everything. Some physicists challenge the likelihood of determinism on the grounds that certain interpretations of quantum mechanics stipulate that the universe is fundamentally indeterministic, such as the Copenhagen interpretation; whereas other interpretations are deterministic, for example, the De Broglie-Bohm Theory and the many-worlds interpretation. Chaos theory describes how a deterministic system can exhibit perplexing behavior that is difficult to predict: as in the butterfly effect, minor variations between the starting conditions of two systems can result in major differences. Yet chaos theory is a wholly determnistic thesis; it merely demonstrates the potential for vastly different consequences from very similar initial conditions. Properly understood, then, it enlightens and reinforces the deterministic claim.
Implications for ethics 
Hard determinists reject free will. Critics often suggest that, in so doing, the hard determinist also rejects ethics. The key to this argument rests on the idea that holding a person morally responsible requires for them to make a choice between two, or more, truly possible alternatives. If choice is indeed impossible, then it would be incorrect to hold anyone morally responsible for his or her actions. If this argument holds, hard determinists are restricted to moral nihilism.
Those hard determinists who defend ethical realism would object to the premise that contra-causal free will is necessary for ethics. Those who are also ethically naturalistic may also point out that there are good reasons to punish criminals: it is a chance to modify their behaviour, or their punishment can act as a deterrent for others who would otherwise act in the same manner. The hard determinist could even argue that this understanding of the true and various causes of a psychopath's behaviour, for instance, allow them to respond even more reasonably or compassionately.
Hard determinists acknowledge that humans do, in some sense, 'choose', or deliberate – although in a way that obeys natural laws. For example, a hard determinist might see humans as a sort of thinking machines, but believe it is inaccurate to say they 'came to a decision' or 'chose'.
Psychological effects of belief in hard determinism 
William James was an American pragmatist philosopher who coined the term "soft determinist" in an influential essay titled The Dilemma of Determinism. He argued against determinism, holding that the important issue is not personal responsibility, but hope. He believed that thorough-going determinism leads either to a bleak pessimism or to a degenerate subjectivism in moral judgment. He proposed the way to escape the dilemma is to allow a role for chance. James was careful to explain that he would rather "debate about objects than words", however. He did not insist in saying that replacing determinism with a model including chance had to mean we had 'free will'.
The determinist would counter-argue that there is still reason for hope. Whether or not the universe is determined does not change the fact that the future is unknown, and might very well always be. From a naturalist point of view, a person's actions still play a role in the shape of that future. Thomas W. Clark, founder and director of the Center for Naturalism, explains that humans are not merely the playthings of patterned, natural forces in the universe - but rather we are ourselves examples of those forces.
In fact, it is even conceivable that it is a lack of belief or understanding of determinism that is likely to cause 'bleak pessimism', or else fatalism (one could suffer from feelings of helplessness). An individual might therefore be enlightened by hard determinism in some sense. By understanding the many factors of a situation that influence their behavior as natural beings, they may obtain better objectivity in their decision making.
See also 
- Vihvelin, Kadri (2011). "Arguments for Incompatibilism". In Edward N. Zalta. The Stanford Encyclopedia of Philosophy (Spring 2011 ed.).
- Raymond J. VanArragon (21 October 2010). Key Terms in Philosophy of Religion. Continuum International Publishing Group. p. 21. ISBN 978-1-4411-3867-5. Retrieved 22 December 2012.
- Philosophy-Dictionary.org on "Hard Determinism"
- Stanford Encyclopedia of Philosophy,"Causal Determinism"
- Chown, Markus (June 1998). "Anything goes". New Scientist 158 (2157).
- James - The Dilemma of Determinism
- Naturalism.org, "Free Will and Naturalism: A Reply to Corliss Lamont"