I. Definition

Do you believe you have free will?  Yet at the same time, if you believe in science then all events have causes, following natural laws; in which case, how can you have free will?  Are not your body and brain physical systems, fully determined by natural law?

Determinism is the philosophy that all events, whether involving inanimate matter or conscious beings like humans, are completely determined by previous events.  In other words, determinism claims that if you knew the physical state of the universe completely at any given moment, and all physical laws, you could (in principle) predict the future perfectly —including the so-called “free” actions of human beings. Therefore, a lot of people think that determinism necessarily denies “free will” (although see section three).

This kind of determinism, the kind most talked about, also called ‘causal determinism’ or ‘physical determinism’ is a fundamental assumption of natural science. The most central idea in this determinism is causality (cause-and-effect); if the universe is purely physical and all physical events are caused, according to natural laws, then it would seem that determinism must be true, or at least so it was believed until quantum mechanics was discovered and threw a wrench into this argument (see section four).

Determinism is one of the biggest issues in both philosophy and physical science; most people, including scientists, want to believe in free will, and most also feel that science implies determinism; meanwhile, modern physics has complicated the issue terribly because quantum mechanics has non-deterministic elements–and it doesn’t justify belief in free will either!

So, at present, determinism remains an unresolved and controversial hypothesis. Is personal psychology determined by nature and or nurture, or is there something like ‘spirit’ which is free? If not, how can we hold people responsible for their actions? How can we punish people for their actions if they don’t have free will? If we are like machines, does morality have any meaning? And if determinism is not true, then what becomes of science? If some events are not determined completely by causality, where do they come from and how can we prove anything?


II. Types of Determinism

Our discussion so far has concerned causal determinism (or physical determinism) which is normally associated with two positions:

  • nomological determinism – the claim that all events are caused by previous events according to rigid laws, such that all events are, in a sense, inevitable.
  • neccesitarianism – that there are no real possibilities; the world could only be as it is.

Predeterminism is the idea that all events are pre-determined, not merely by their immediate causes, but since the beginning of time.  This seems to be implied by causal determinism, since whatever happened at the beginning of time would determine the chain of cause and effect ever after.

Fatalism is the non-scientific version of predeterminism, claiming that we all have unavoidable fates, but not ones which are necessarily based on natural law, allowing for other sources of fate, such as God.

Theological determinism this is the idea either that God has determined our fates, or that God knows what they are, which would also imply that they cannot be changed.

Adequate determinism is probably the operating philosophy of most scientists today—the idea that although quantum reality is partly non-deterministic, it is deterministic enough, for all practical purposes, because the unpredictability averages out at the human scale.

The Many Worlds Interpretation of Quantum Mechanics this theory, developed by John Wheeler and Hugh Everett III, may be a way to return complete determinism to quantum mechanics.  According to this theory, when you observe a quantum system and get a random result, what actually happened was that you and the system you observed went into all of the possible states—each in a different parallel universe. The you in this universe seems to get one random result and the you in another universe seems to get another random result, but all together, all of the possible results happened, each to a different you.  This might sound like desperately crazy way to put determinism back in QM but actually, it’s the most unbiased interpretation of the theory; scientists who do not believe in the multiple worlds interpretation are forced to hypothesize other unexplainable processes, like “wave collapse” in order to make QM work.

Biological determinism, Cultural determinism, and Environmental determinism: these three ideas are about determinism in a different sense than in most of this article; they each claim that one thing, either biology, culture, or environment, determines who a person becomes, psychologically.

Linguistic determinism is the idea that the grammar and vocabularies of human languages limit the ways we can think and perceive the world.


III. Determinism versus Free Will

You might think these are opposites; however, philosophers recognize four possible points of view regarding the two—both true, both false, and one or the other.  Compatibilism, the theory that they can both be true at the same time, is popular, since most people want to believe in both.  Then again, the theory that they are both false is also popular; because that is what current science seems to imply:

  • if quantum theory is correct, determinism is probably false
  • if neuroscience is correct, free will is probably false

As far as we know, our minds are entirely part of our brains, which simply obey the laws of physics. So, how could the activity of our brains not be determined by physical law?  Quantum theory doesn’t help, because even if quantum events in our brain are un-determined, they’re random; random is just as much the opposite of free will as deterministic!

But, of course, philosophers are always coming up with new ways to justify belief in determinism and / or free will—so there are lots of debates to be had and the jury is still out!

One promising idea for allowing free will into natural law comes from the theory of complex systems – the idea of emergence.  Emergence is when something new appears in nature, something which could not have been predicted due to its complexity, like weather events.  Your brain might be deterministic (at least to a quantum degree) yet nevertheless unpredictable due to its complexity. Whether this makes free will possible or not is still an open question.


IV. Controversies about Determinism

Does quantum mechanics necessarily mean that the universe is non-deterministic?

The laws of quantum mechanics (QM), the most thoroughly proven theory of all time, deny that specific events are predictable or determined at the quantum scale (smaller than an atom).  According to QM, only the probabilities of events are determined, while specific events are random.  Whether an atom will decay at a certain time, or where on a photographic plate a photon will hit, can never be predicted, no matter how much you know about previous events, except statistically.  You can say approximately how many photons out of 100 will hit a certain spot, but not which ones.  And the uncertainty is not just a matter of human knowledge; the photons do not follow specific paths, and have no specific locations, until they are observed, and there is no way to predict exactly where they will be.

Most philosophers do not worry much about quantum theory because they have been told that it doesn’t matter at the human scale; although quantum events may be non-deterministic, their probabilities average out to give precisely the predictions of Newtonian physics for events much larger than atoms. But, although this is true in principle, it’s not really true. For one thing, quantum theory operates at every scale, even if its randomness averages out at large scales, and for another thing, it has now been shown that quantum effects are amplified up to the biological scale by chaos; some biological processes—such as the formation of proteins–even rely on quantum indetermninacy!

Chaos theory shows that quantum effects can matter at the scale of neurons in the brain, which means that quantum indeterminism could be relevant to the question of whether our choices are determined or not.  However, this does not make quantum indeterminacy a source of free will because randomness is no more free will than determinism, is it?!

And while quantum indeterminism, if true, may be relevant to human cognition, there are still alternative theories trying to put determinism back into the quantum.  According to these ‘hidden variable theories,’ quantum events only appear random because we cannot see the hidden processes which determine them.  However, at the present time, most physicists believe that hidden variable theories have been ruled out by experiments on ‘quantum entanglement’ which seem to show that any such hidden processes would need to operate faster than the speed of light.

There are many more issues in this debate that we cannot present here.  So, we shall only summarize, that quantum mechanics seems to prove that the world is only statistically, or probabilistically deterministic, and deeply random at the smallest scales, yet quantum mechanics itself is full of debates which might someday change that conclusion, and either way, it doesn’t seem to provide a basis for free will.


V. Quotes about Determinism

Quote #1:

The assumption of an absolute determinism is the essential foundation of every scientific enquiry.” — Max Planck

In this quotation, Max Planck, one of quantum theory’s founders, ironically asserts that absolute determinism must be at the foundation of every scientific theory.  Albert Einstein and many others have shared this view and refused to accept quantum indeterminism.  They refuse because the possibility of scientific truth seems to depend on predictability; if certain causes don’t always lead to certain effects, how can anything be proven? Nevertheless, efforts to remove indeterminacy from quantum theory have failed, and science has not fallen apart; probabilities have proven workable so far.

Quote #2:

“Man can do what he wills but he cannot will what he wills.” — Arthur Schopenhauer

In this incredibly pithy statement, Schopenhauer distinguishes between a way in which we are free and a way in which we are not.  Whether determinism is true or not, we do as we will, in the everyday sense, all the time.  Yet, unless our understanding of nature is very wrong, we cannot choose our psychology; what we “will” is what we were born and raised and shaped to will, by our genes and our experiences.

VI. Determinism in Pop Culture

Example #1: The Matrix

Ever a rich source of philosophy, the Matrix films touched on determinism in many ways, none more so than through the character of the Oracle, a piece of living software that appears to the hero as a wise motherly figure who can see the future.  The Matrix take on determinism is exactly that implied by the philosophy of artificial intelligence – that all events and choices are pre-determined as if created by software in a machine. And this is one of the most recent speculations about the nature of reality – that reality is either literally a software simulation, or that the universe is like a computer and natural law like software.

Example #2: Minority Report

Minority Report was one of the many blockbuster films based on the works of Philip K. Dick, the most philosophically significant science-fiction author of the twentieth century.  This film deals directly and dramatically with the conflict between free will and determinism; future murders can be reliably predicted and therefore stopped—by arresting the murderers before they kill.  But if they can do that, then it means that the murders were not pre-determined, so how can we justify incarcerating the would-be murderers?  You can always rely on P.K. Dick for a brain-buster!


VII. The History of Determinism

Perhaps the earliest beliefs about determinism can be seen in the ancient practice of divination (‘fortune telling’) which assumes that the future is foreseeable—however, supernaturally so.  It is difficult to think of a culture which has not engaged in some form of divination, such as reading animal entrails, tea leaves, tarot cards, or palms.

One of the most philosophically sophisticated forms of divination was the ancient Chinese I Ching, an expression of Taoist philosophy, whose origins are lost in pre-history.  Although the I Ching is most well-known as a form of fortune telling, it is also a system of philosophy concerning cause-and-effect and the ‘theory of yin and yang.’  The I Ching is a system for analyzing the patterns of cause-and-effect in the world, assuming that they can be understood in terms of the inter-transformations (the ‘changes’) of yin and yang, which are the two complementary and opposite aspects of all things (up / down, in / out, active / passive, etc.).

Most people thousands of years ago believed that events were determined by spirits or gods, but Taoists are atheists, believing that yin and yang simply describe the nature of all things. The I Ching is probably the first book to present a cogent theory of natural determinism.

The Maya people of Central America provide another example of ancient determinism.  In ancient Mayan culture, science, especially astronomy, was thoroughly blended with religion.  And both were heavily concerned with predicting important natural and cultural events, which were thought to be determined by cycles of time.  The Maya kept track of many different astronomical cycles, and some cycles with no known natural sources.  They wrote books—almanacs—in which they calculated when astronomical events would occur (such as eclipses) and also how they should run their lives—whether a certain day in a cycle was a good day for planting, or getting married, etc.  The Maya believed that the ‘fortune’ for a particular day was determined by its place in all of these deterministic cycles of time.

Another ancient determinism is ‘karma,’ originally a feature of Hinduism, inherited by Buddhism, and then finally spread throughout the western world by hippies and new age thinkers!  Karma may seem like a supernatural and superstitious belief, or a rational and scientific one, depending on how you interpret it.  In the supernatural interpretations, karma is a spiritual law of nature — that your actions in this life determine what happens to you after death, whether you reincarnate as a worm, or a rich person with no worries. However, karma can also be interpreted as a natural law merely saying that whatever you do has consequences (that tend to come back to you).  So, this is another kind of determinism, not one which denies free will, and one which may or may not be compatible with science.

The earliest western notion of determinism comes from the Greek Stoics who believed in physical causal determinism; this resulted in the first known debates over determinism versus free will, in the works of Alexander of Aphrodisias, in the 1st-3rd centuries C.E.

Science and philosophy after the dark ages quickly came to the ‘Newtonian’ world-view, named after Isaac Newton, who did not invent the world-view, but supported it perhaps better than any previous scientist, in which all natural events are physical and governed by entirely deterministic laws of cause and effect.  This world-view has held powerful sway over philosophy and science since Newton’s time because it has proven true in experiment after experiment, and has enabled human beings to discover and exploit natural law in astounding ways over the past few hundred years. Newtonian determinism seemed unquestionable to most scientists until the discovery of quantum mechanics, and most people who aren’t aware of quantum mechanics still hold the Newtonian world-view.


Which of the following are normally assumed in determinism?





Which of the following are absolutely, necessarily, in conflict with determinism?





Why is quantum mechanics in conflict with determinism?





Which of the following does modern science imply about determinism?





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