Determinism is the philosophical proposition that every event, including human cognition, behavior, decision, and action, is causally determined by an unbroken chain of prior occurrences. With numerous historical debates, many varieties and philosophical positions on the subject of determinism exist from traditions throughout the world.
Philosophy of determinism
Determinism necessarily entails that humanity or individual humans may not change the course of the future and its events (a position known as fatalism); however, some determinists believe that the level to which human beings have influence over their future is itself merely dependent on present and past. Causal determinism is associated with, and relies upon, the ideas of materialism and causality. Some of the main philosophers who have dealt with this issue are Marcus Aurelius, Omar Khayyám, Thomas Hobbes, Baruch Spinoza, Gottfried Leibniz, David Hume, Baron d'Holbach (Paul Heinrich Dietrich), Pierre-Simon Laplace, Arthur Schopenhauer, William James, Friedrich Nietzsche, Albert Einstein, Niels Bohr, and, more recently, John Searle, Ted Honderich, and Daniel Dennett.
Mecca Chiesa notes that the probabilistic or selectionistic determinism of B.F. Skinner comprised a wholly separate conception of determinism that was not mechanistic at all. A mechanistic determinism would assume that every event has an unbroken chain of prior occurrences, but a selectionistic or probabilistic model does not.
The nature of determinism
The exact meaning of the term determinism has historically been subject to rigorous scrutiny and several interpretations. Some people, called Incompatibilists, view determinism and free will as mutually exclusive. The belief that free will is an illusion is known as Hard Determinism. Others, labeled Compatibilists, (or Soft Determinists) believe that the two ideas can be coherently reconciled. Incompatibilists who accept free will but reject determinism are called Philosophical Libertarians — not to be confused with Political Libertarians. Some feel it refers to the metaphysical truth of independent agency, whereas others simply define it as the feeling of agency that humans experience when they act. Many will agree that determinism is the theory that human choices and actions can be determined from external causes; but free will is the theory that human choices and actions are determined by internal causes: that an individual is the prime mover of his life.
Ted Honderich, in his book How Free Are You? - The Determinism Problem gives the following summary of the theory of determinism:
In its central part, determinism is the theory that our choices and decisions and what gives rise to them are effects. What the theory comes to therefore depends on what effects are taken to be... [I]t is effects that seem fundamental to the subject of determinism and how it affects our lives.
Varieties of determinism
Causal (or nomological) determinism is the thesis that future events are necessitated by past and present events combined with the laws of nature. Such determinism is sometimes illustrated by the thought experiment of Laplace's demon. Imagine an entity that knows all facts about the past and the present, and knows all natural laws that govern the universe. Such an entity might be able to use this knowledge to foresee the future, down to the smallest detail. Simon-Pierre Laplace's determinist "dogma" (as described by Stephen Hawking) is generally referred to as "scientific determinism" and predicated on the supposition that all events have a cause and effect and the precise combination of events at a particular time engender a particular outcome. This causal determinism has a direct relationship with predictability. Perfect predictability implies strict determinism, but lack of predictability does not necessarily imply lack of determinism. Limitations on predictability could alternatively be caused by factors such as a lack of information or excessive complexity. An example of this could be found by looking at a bomb dropping from the air. Through mathematics, we can predict the time the bomb will take to reach the ground, and we also know what will happen once the bomb explodes. Any small errors in prediction might arise from our not measuring some factors, such as puffs of wind or variations in air temperature along the bomb's path.
Logical determinism is the notion that all propositions, whether about the past, present or future, are either true or false. The problem of free will, in this context, is the problem of how choices can be free, given that what one does in the future is already determined as true or false in the present. This is referred to as the problem of future contingents.
Additionally, there is environmental determinism, also known as climatic or geographical determinism which holds the view that the physical environment, rather than social conditions, determines culture. Those who believe this view say that humans are strictly defined by stimulus-response (environment-behavior) and cannot deviate. Key proponents of this notion have included Ellen Churchill Semple, Ellsworth Huntington, Thomas Griffith Taylor and possibly Jared Diamond, although his status as an environmental determinist is debated.
Biological determinism is the idea that all behavior, belief, and desire are fixed by our genetic endowment. There are other theses on determinism, including cultural determinism and the narrower concept of psychological determinism. Combinations and syntheses of determinist theses, e.g. bio-environmental determinism, are even more common. Addiction Specialist Dr. Drew Pinski relates addiction to biological determinism:
"Absolutely. It's a complex disorder, but it clearly has a genetic basis. In fact, in the definition of the disease, we consider genetics absolutely a crucial piece of the definition. So the definition as stated in a consensus conference that was published in the early '90s, it's a genetic disorder with a biological basis. The hallmark is the progressive use in the face of adverse consequence, and then finally denial."
Theological determinism is the thesis that there is a God who determines all that humans will do, either by knowing their actions in advance, via some form of omniscience or by decreeing their actions in advance. The problem of free will, in this context, is the problem of how our actions can be free, if there is a being who has determined them for us ahead of time.
Determinism with regard to ethics
Often determinism is connected with ethics as an excuse for unethical actions. Hard determinists assert morality as being caused through hereditary and environmental means. Opposition to determinism promotes that without belief in uncaused free will, humans will not have reason to behave ethically. Determinism, however, does not negate emotions and reason of a person, it simply proposes the source of what causes us to fall back on moral behavior. Anyone susceptible to immoral actions from the idea of determinism was susceptible before and does not hold strong moral judgment prior to the idea. Determinism implies the moral differences between two people are caused by hereditary predispositions and environmental effects and events. This does not mean determinists are against punishment of people who commit crimes because the cause of a person's morality (depending on the branch of determinism) is not necessarily themselves.
Determinism in Eastern tradition
The idea that the entire universe is a deterministic system has been articulated in both Eastern and non-Eastern religion, philosophy, and literature. A shifting flow of probabilities for futures lies at the heart of theories associated with the Yi Jing (or I Ching, the Book of Changes). Probabilities take the center of the stage away from things and people. A kind of "divine" volition sets the fundamental rules for the working out of probabilities in the universe, and human volitions are always a factor in the ways that humans can deal with the real world situations one encounters. If one's situation in life is surfing on a tsunami, one still has some range of choices even in that situation. One person might give up, and another person might choose to struggle and perhaps to survive. The Yi Jing mentality is much closer to the mentality of quantum physics than to that of classical physics, and also finds parallelism in voluntarist or Existentialist ideas of taking one's life as one's project. This theory has also seen its use in popular culture in Japan. In an anime titled xxxHolic the term Hitsuzen is used to describe the Determinism theory although it has a more magical feel to its explanation. 
In the philosophical schools of India, the concept of precise and continual effect of laws of Karma on the existence of all sentient beings is analogous to western deterministic concept. Karma is the concept of "action" or "deed" in Indian religions. It is understood as that which causes the entire cycle of cause and effect (i.e., the cycle called saṃsāra) originating in ancient India and treated in Hindu, Jain, Sikh and Buddhist philosophies. Karma is considered predetermined and deterministic in the universe, with the exception of a human, who through free will can (somewhat) influence the future.
Determinism in Western tradition
In the West, the Ancient Greek atomists Leucippus and Democritus were the first to anticipate determinism when they theorized that all processes in the world were due to the mechanical interplay of atoms, but this theory did not gain much support at the time. Determinism in the West is often associated with Newtonian physics, which depicts the physical matter of the universe as operating according to a set of fixed, knowable laws. The "billiard ball" hypothesis, a product of Newtonian physics, argues that once the initial conditions of the universe have been established, the rest of the history of the universe follows inevitably. If it were actually possible to have complete knowledge of physical matter and all of the laws governing that matter at any one time, then it would be theoretically possible to compute the time and place of every event that will ever occur (Laplace's demon). In this sense, the basic particles of the universe operate in the same fashion as the rolling balls on a billiard table, moving and striking each other in predictable ways to produce predictable results.
Whether or not it is all-encompassing in so doing, Newtonian mechanics deals only with caused events, e.g.: If an object begins in a known position and is hit dead on by an object with some known velocity, then it will be pushed straight toward another predictable point. If it goes somewhere else, the Newtonians argue, one must question one's measurements of the original position of the object, the exact direction of the striking object, gravitational or other fields that were inadvertently ignored, etc. Then, they maintain, repeated experiments and improvements in accuracy will always bring one's observations closer to the theoretically predicted results. When dealing with situations on an ordinary human scale, Newtonian physics has been so enormously successful that it has no competition. But it fails spectacularly as velocities become some substantial fraction of the speed of light and when interactions at the atomic scale are studied. Before the discovery of quantum effects and other challenges to Newtonian physics, "uncertainty" was always a term that applied to the accuracy of human knowledge about causes and effects, and not to the causes and effects themselves.
Newtonian mechanics as well as any following physical theories are results of observations, and experiments and so they describe "how it all works" within a tolerance. However, old western scientists believed if there are any logical connections found between an observed cause and effect, there must be also some absolute natural laws behind. Belief in perfect natural laws driving everything, instead of just describing what we should expect, led to searching for a set of universal simple laws that rule the world. This movement significantly encouraged deterministic views in western philosophy.
Minds and bodies
Some determinists argue that materialism does not present a complete understanding of the universe, because while it can describe determinate interactions among material things, it ignores the minds or souls of conscious beings. A number of positions can be delineated:
- Immaterial souls exist and exert a non-deterministic causal influence on bodies. (Traditional free-will, interactionist dualism).
- Immaterial souls exist, but are part of deterministic framework.
- Immaterial souls exist, but exert no causal influence, free or determined (epiphenomenalism, occasionalism)
- Immaterial souls do not exist — the mind-body problem has some other solution.
- Immaterial souls are all that exist (Idealism).
Modern perspectives on determinism
Determinism and a first cause
Since the early twentieth century when astronomer Edwin Hubble first hypothesized that redshift shows the universe is expanding, prevailing scientific opinion has been that the current state of the universe is the result of a process described by the Big Bang. Many theists and deists claim that it therefore has a finite age, pointing out that something cannot come from nothing. The big bang does not describe from where the compressed universe came; instead it leaves the question open. Different astrophysicists hold different views about precisely how the universe originated (Cosmogony). The philosophical argument here would be that the big bang triggered every single action, and possibly mental thought, through the system of cause and effect.
Determinism and generative processes
Some proponents of emergentist or generative philosophy, cognitive sciences and evolutionary psychology, argue that free will does not exist. They suggest instead that an illusion of free will is experienced due to the generation of infinite behaviour from the interaction of finite-deterministic set of rules and parameters. Thus the unpredictability of the emerging behaviour from deterministic processes leads to a perception of free will, even though free will as an ontological entity does not exist.
As an illustration, the strategy board-games chess and Go have rigorous rules in which no information (such as cards' face-values) is hidden from either player and no random events (such as dice-rolling) happen within the game. Yet, chess and especially Go with its extremely simple deterministic rules, can still have an extremely large number of unpredictable moves. By this analogy, it is suggested, the experience of free will emerges from the interaction of finite rules and deterministic parameters that generate infinite and unpredictable behaviour. Yet, if all these events were accounted for, and there were a known way to evaluate these events, the seemingly unpredictable behaviour would become predictable.
Determinism in mathematical models
Many mathematical models are deterministic. This is true of most models involving differential equations (notably, those measuring rate of change over time). Mathematical models that are not deterministic because they involve randomness are called stochastic. Because of sensitive dependence on initial conditions, some deterministic models may appear to behave non-deterministically; in such cases, a deterministic interpretation of the model may not be useful due to numerical instability and a finite amount of precision in measurement. Such considerations can motivate the consideration of a stochastic model when the underlying system is accurately modeled in the abstract by deterministic equations. A truly non-deterministic event is independent of the time and observer, thus it is called intrinsic random event.
Arguments against determinism
Determinism, quantum mechanics, and classical physics
Since the beginning of the 20th century, quantum mechanics has revealed previously concealed aspects of events. Newtonian physics, taken in isolation rather than as an approximation to quantum mechanics, depicts a universe in which objects move in perfectly determinative ways. At human scale levels of interaction, Newtonian mechanics makes predictions that are agreed with, within the accuracy of measurement. Poorly designed and fabricated guns and ammunition scatter their shots rather widely around the center of a target, and better guns produce tighter patterns. Absolute knowledge of the forces accelerating a bullet should produce absolutely reliable predictions of its path, or so was thought. However, knowledge is never absolute in practice and the equations of Newtonian mechanics can exhibit sensitive dependence on initial conditions, meaning small errors in knowledge of initial conditions can result in arbitrarily large deviations from predicted behavior.
At atomic scales the paths of objects can only be predicted in a probabilistic way. The paths may not be exactly specified in a full quantum description of the particles; "path" is a classical concept which quantum particles do not exactly possess. The probability arises from the measurement of the perceived path of the particle. In some cases, a quantum particle may trace an exact path, and the probability of finding the particles in that path is one. The quantum development is at least as predictable as the classical motion, but it describes wave functions that cannot be easily expressed in ordinary language. In double-slit experiments, photons are fired singly through a double-slit apparatus at a distant screen and do not arrive at a single point, nor do the photons arrive in a scattered pattern analogous to bullets fired by a fixed gun at a distant target. Instead, the light arrives in varying concentrations at widely separated points, and the distribution of its collisions with the target can be calculated reliably. In that sense the behavior of light in this apparatus is deterministic, but there is no way to predict where in the resulting interference pattern an individual photon will make its contribution (see Heisenberg Uncertainty Principle).
Some have argued that, in addition to the conditions humans can observe and the laws we can deduce, there are hidden factors or "hidden variables" that determine absolutely in which order photons reach the detector screen. They argue that the course of the universe is absolutely determined, but that humans are screened from knowledge of the determinative factors. So, they say, it only appears that things proceed in a merely probabilistically-determinative way. In actuality, they proceed in an absolutely deterministic way. Although matters are still subject to some measure of dispute, quantum mechanics makes statistical predictions which would be violated if some local hidden variables existed. There have been a number of experiments to verify those predictions, and so far they do not appear to be violated, though many physicists believe better experiments are needed to conclusively settle the question. (See Bell test experiments.) It is possible, however, to augment quantum mechanics with non-local hidden variables to achieve a deterministic theory that is in agreement with experiment. An example is the Bohm interpretation of quantum mechanics.
On the macro scale it can matter very much whether a bullet arrives at a certain point at a certain time, as snipers are well aware; there are analogous quantum events that have macro- as well as quantum-level consequences. It is easy to contrive situations in which the arrival of an electron at a screen at a certain point and time would trigger one event and its arrival at another point would trigger an entirely different event. (See Schrödinger's cat.)
Even before the laws of quantum mechanics were fully developed, the phenomenon of radioactivity posed a challenge to determinism. A gram of uranium-238, a commonly occurring radioactive substance, contains some 2.5 x 1021 atoms. By all tests known to science these atoms are identical and indistinguishable. Yet about 12600 times a second one of the atoms in that gram will decay, giving off an alpha particle. This decay does not depend on external stimulus and no extant theory of physics predicts when any given atom will decay, with realistically obtainable knowledge. The uranium found on earth is thought to have been synthesized during a supernova that occurred roughly 5 billion years ago. For determinism to hold, every uranium atom must contain some internal "clock" that specifies the exact time it will decay. And somehow the laws of physics must specify exactly how those clocks were set as each uranium atom was formed during the supernova collapse.
Exposure to alpha radiation can cause cancer. For this to happen, at some point a specific alpha particle must alter some chemical reaction in a cell in a way that results in a mutation. Since molecules are in constant thermal motion, the exact timing of the radioactive decay that produced the fatal alpha particle matters. If probabilistically determined events do have an impact on the macro events—such as when a person who could have been historically important dies in youth of a cancer caused by a random mutation—then the course of history is not predictable from the dawn of time.
The time dependent Schrödinger equation gives the first time derivative of the quantum state. That is, it explicitly and uniquely predicts the development of the wave function with time.
So quantum mechanics is deterministic, provided that one accepts the wave function itself as reality (rather than as probability of classical coordinates). Since we have no practical way of knowing the exact magnitudes, and especially the phases, in a full quantum mechanical description of the causes of an observable event, this turns out to be philosophically similar to the "hidden variable" doctrine.
According to some, quantum mechanics is more strongly ordered than Classical Mechanics, because while Classical Mechanics is chaotic, quantum mechanics is not. For example, the classical problem of three bodies under a force such as gravity is not integrable, while the quantum mechanical three body problem is tractable and integrable, using the Faddeev Equations. That is, the quantum mechanical problem can always be solved to a given accuracy with a large enough computer of predetermined precision, while the classical problem may require arbitrarily high precision, depending on the details of the motion. This does not mean that quantum mechanics describes the world as more deterministic, unless one already considers the wave function to be the true reality. Even so, this does not get rid of the probabilities, because we can't do anything without using classical descriptions, but it assigns the probabilities to the classical approximation, rather than to the quantum reality.
Asserting that quantum mechanics is deterministic by treating the wave function itself as reality implies a single wave function for the entire universe, starting at the origin of the universe. Such a "wave function of everything" would carry the probabilities of not just the world we know, but every other possible world that could have evolved. For example, large voids in the distributions of galaxies are believed by many cosmologists to have originated in quantum fluctuations during the big bang. (See cosmic inflation and primordial fluctuations.) If so, the "wave function of everything" would carry the possibility that the region where our Milky Way galaxy is located could have been a void and the Earth never existed at all. (See large-scale structure of the cosmos.)
Intrinsic to the debate concerning determinism is the issue of first cause. Deism, a philosophy articulated in the seventeenth century, holds that the universe has been deterministic since creation, but ascribes the creation to a metaphysical God or first cause outside of the chain of determinism. God may have begun the process, Deism argues, but God has not influenced its evolution. This perspective illustrates a puzzle underlying any conception of determinism:
Assume: All events have causes, and their causes are all prior events. There is no cycle of events such that an event (possibly indirectly) causes itself. The picture this gives us is that Event AN is preceded by AN-1, which is preceded by AN-2, and so forth. Under these assumptions, two possibilities seem clear, and both of them question the validity of the original assumptions:
(1) There is an event A0 prior to which there was no other event that could serve as its cause. (2) There is no event A0 prior to which there was no other event, which means that we are presented with an infinite series of causally related events, which is itself an event, and yet there is no cause for this infinite series of events.
Under this analysis the original assumption must have something wrong with it. It can be fixed by admitting one exception, a creation event (either the creation of the original event or events, or the creation of the infinite series of events) that is itself not a caused event in the sense of the word "caused" used in the formulation of the original assumption. Some agency, which many systems of thought call God, creates space, time, and the entities found in the universe by means of some process that is analogous to causation but is not causation as we know it. This solution to the original difficulty has led people to question whether there is any reason for there only being one divine quasi-causal act, whether there have not been a number of events that have occurred outside the ordinary sequence of events, events that may be called miracles, or accidents.
Another possibility is that the "last event" loops back to the "first event" causing an infinite loop. If you were to call the Big Bang the first event, you would see the end of the Universe as the "last event". In theory, the end of the Universe would be the cause of the beginning of the Universe. You would be left with an infinite loop of time with no real beginning or end. This theory eliminates the need for a first cause, but does not explain why there should be a loop in time. A further problem is that an infinite series of events before any particular event would make it impossible for the event to occur. If there are an infinite number of yesterdays, how do you get to today?
Immanuel Kant carried forth this idea of Leibniz in his idea of transcendental relations, and as a result, this had profound effects on later philosophical attempts to sort these issues out. His most influential immediate successor, a strong critic whose ideas were yet strongly influenced by Kant, was Edmund Husserl, the developer of the school of philosophy called phenomenology. But the central concern of that school was to elucidate not physics but the grounding of information that physicists and others regard as empirical. In an indirect way, this train of investigation appears to have contributed much to the philosophy of science called logical positivism and particularly to the thought of members of the Vienna Circle, all of which have had much to say, at least indirectly, about ideas of determinism.
- Van Inwagen, Peter, 1983, An Essay on Free Will, Oxford: Clarendon Press.
- Chiesa, Mecca (2004) Radical Behaviorism: The Philosophy & The Science.
- Ringen, J. D. (1993). Adaptation, teleology, and selection by consequences. Journal of Applied Behavior Analysis. 60,3–15. 
- Honderich, Ted (1993) How Free Are You? - The Determinism Problem page 6, Oxford University Press. ISBN 0-19-283139-9
- Suppes, P., 1993, “The Transcendental Character of Determinism,” Midwest Studies in Philosophy, 18: 242–257.
- Hawking, Stephen. "Does God Play Dice?". Retrieved on 2008-11-16.
- Andrew, Sluyter (2003). "Neo-Environmental Determinism, Intellectual Damage Control, and Nature/Society Science". Antipode 4 (35): 813–817.
- Fischer, John Martin (1989) God, Foreknowledge and Freedom. Stanford, CA: Stanford University Press. ISBN 1-55786-857-3
- Watt, Montgomery (1948) Free-Will and Predestination in Early Islam. London:Luzac & Co.
- Swartz, Norman (2003) The Concept of Physical Law / Chapter 10: Free Will and Determinism ( https://www.sfu.ca/philosophy/physical-law/)
- By 'soul' in the context of (1) is meant an autonomous immaterial agent that has the power to control the body but not to be controlled by the body (this theory of determinism thus conceives of conscious agents in dualistic terms). Therefore the soul stands to the activities of the individual agent's body as does the creator of the universe to the universe. The creator of the universe put in motion a deterministic system of material entities that would, if left to themselves, carry out the chain of events determined by ordinary causation. But the creator also provided for souls that could exert a causal force analogous to the primordial causal force and alter outcomes in the physical universe via the acts of their bodies. Thus, it emerges that no events in the physical universe are uncaused. Some are caused entirely by the original creative act and the way it plays itself out through time, and some are caused by the acts of created souls. But those created souls were not created by means of physical processes involving ordinary causation. They are another order of being entirely, gifted with the power to modify the original creation. However, determinism is not necessarily limited to matter; it can encompass energy as well. The question of how these immaterial entities can act upon material entities is deeply involved in what is generally known as the mind-body problem. It is a significant problem which philosophers have not reached agreement about
- Free Will (Stanford Encyclopedia of Philosophy)
- Kenrick, D. T., Li, N. P., & Butner, J. 2003; Nowak A., Vallacher R.R., Tesser A., Borkowski W., 2000;
- Epstein J.M. and Axtell R. 1996; Epstein J.M. 1999
- J. Glimm, D. Sharp, Stochastic Differential Equations: Selected Applications in Continuum Physics, in: R.A. Carmona, B. Rozovskii (ed.) Stochastic Partial Differential Equations: Six Perspectives, American Mathematical Society (October 1998) (ISBN 0821808060).
References and bibliography
- Albert Messiah, Quantum Mechanics, English translation by G. M. Temmer of Mécanique Quantique, 1966, John Wiley and Sons, vol. I, chapter IV, section III.
- A lecture to his statistical mechanics class at the University of California at Santa Barbara by Dr. Herbert P. Broida 4 (1920–1978) (a well known experimental physicist)
- Dennett D. (2003) Freedom Evolves. Viking Penguin, NY, USA.
- "Physics and the Real World" by George F. R. Ellis, Physics Today, July, 2005
- Kenrick, D. T., Li, N. P., & Butner, J. (2003). Dynamical evolutionary psychology: Individual
decision rules and emergent social norms. Psychological Review, 110, 3–28
- Nowak A., Vallacher R.R., Tesser A., Borkowski W., (2000) Society of Self: The emergence of collective properties in self-structure. Psychological Review 107
- Epstein J.M. and Axtell R. (1996) Growing Artificial Societies — Social Science from the Bottom. Cambridge MA, MIT Press.
- Epstein J.M. (1999) Agent Based Models and Generative Social Science. Complexity, IV (5)
- Can you show me the way to the human soul? Thanks!
- Stanford Encyclopedia of Philosophy entry on Causal Determinism
- Determinism in History from the Dictionary of the History of Ideas
- Philosopher Ted Honderich's Determinism web resource
- An Introduction to Free Will and Determinism by Paul Newall, aimed at beginners.
- The Society of Natural Science
- Determinism and Free Will in Judaism
- Snooker, Pool, and Determinism