Determinism can be defined in different ways. In the Stanford Encyclopedia of Philosophy, determinism is described as follows: “the world is governed by (or is under the sway of) determinism if and only if, given a specified way things are at a time t, the way things go thereafter is fixed as a matter of natural law.”1 The Big Questions in Free Will Lexicon of Key Terms defines it as “the thesis that a complete statement of the laws of nature together with a complete description of the entire universe at any point in time logically entails a complete description of the entire universe at any other point in time.”2 In other words, if you have a complete description of the entire universe at one point, you can get a complete description of the universe in the past or future by calculating in the complete laws of nature (in theory).
According to these definitions, determinism implicitly includes the concepts of pan-causality, reductionism, and fatalism. What is meant by “pan-causality” is simply that every event or thing in the universe has a cause. “Reductionism” means that higher-level systems are reducible to lower-level systems. For example, reductionists believe the human mind is reducible to the firing of neurons in the brain and physical and chemical processes in the brain or the “behaviors” of molecules and atoms. As for “fatalism,”The Stanford Encyclopedia of Philosophy states “philosophers usually use the word to refer to the view that we are powerless to do anything other than what we actually do.”3 Given these included concepts in the larger concept of determinism, it becomes apparent with some thought that free will as conventionally conceived (the ability to do other than what was done) is not compatible with determinism.

Let’s first consider pan-causality. If every event and thing has a cause, then it becomes necessary to question whether these causes are necessary causes, sufficient causes, or just contributory causes. A is a necessary cause of B if B necessarily implies the presence of A. For example, oxygen is a necessary cause of aerobic life. You cannot have aerobic life without oxygen. However, just because there is oxygen doesn’t necessitate that there will be aerobic life. This must have been the case in the early evolution of our planet. However, aerobic life soon arose after oxygen came into the atmosphere. On the other hand, A is a sufficient cause of B if A necessarily implies the presence of B. For example, the sun is a sufficient cause of light. The sun necessarily implies light. However, you can have light without the sun (starlight, lamplight, candles, etc.). So, the sun is a sufficient cause of light, but it is not a necessary cause of light. Lastly, a cause is contributory if it contributes to the effect, but it need not be a necessary or sufficient cause. For example, financial ruin may be a contributory cause of someone’s suicide but it is neither sufficient nor necessary. Someone may face financial ruin and not commit suicide. So, it is not a sufficient cause of suicide. Likewise, it is not a necessary cause of suicide as a rich person with no financial troubles may commit suicide due to other factors. The conventional conception of free will (the ability to do otherwise) generally attributes contributory causes to our actions that are neither sufficient nor necessary causes. If all the causes of our decisions were merely contributory, then this would leave room available in our universe for the conventional conception of free will. Determinism denies that the true causes of our decisions are contributory causes that are neither sufficient nor necessary.

However, determinism is much more than just pan-causality. If higher-level events are reducible to lower-level events down to physical-chemical processes, then events such as human decisions are reducible to the “behaviors” of atomic and subatomic particles and the four forces of nature: electromagnetism, gravity, and the weak and strong nuclear forces. The conventional concept of causality is not sufficient to explain the workings of physics, as the objects of physics are explained in a more relational way than in a “one precedes or causes the other” way. Take for example the presence of the Moon and the tides. It is not accurate to say that the Moon causes the tides. It is more of a relation between the Earth and the Moon. It is not easy to put this relation in the ordinary language of cause and effect. It is not so much that the Moon exerts a gravitational pull on the Earth’s oceans and then that causes the tides. This would be an inaccurate statement. It is more of a relationship between the gravitational pulls of both the Earth and the Moon. (Despite what Bill O’Reilly might think: http://www.huffingtonpost.com/2011/01/06/oreilly-god-causes-tides_n_805262.html.) Hence, the interactions and processes on the molecular, atomic, and subatomic level in our brains is a relational one with the rest of the molecular, atomic, and subatomic functions in the environment. However, when “looking” at this level, there really is no distinction between my body and the environment. Particles and forces interact and there is no clear border where the body ends and the environment begins. As such, the universe as a whole is entirely connected by the forces of nature. Even in an indeterministic universe, the forces of nature that occur on the molecular, atomic, and subatomic level determine what happens on the higher, “more complex” human macro-level. So, there is no room for the conventional conception of free will if reductionism is true.

As for fatalism, the view that we are powerless to do anything other than what we actually do, it follows from what was explained above that if reductionism is true, then we have no control over our decisions. Our decisions are merely a function of physical and chemical laws. Hence, it follows that whatever we do we have no control over. Although in an indeterministic universe, there are different possible futures (with some presumably more probable than others), our decisions are still just functions of physical and chemical processes in the brain (according to reductionists). It may be possible to conceive in an indeterministic universe that I could have done otherwise because in such a universe atomic and subatomic particles “behave” according to probabilities. Different degrees of probabilities entail different possible futures. However, if reductionism is a truth about the universe, and even if there is some indeterminism in the universe, then I cannot have any control over my future as these probabilities are a function of nature, not a function of me. Hence, fatalism holds if reductionism is true.
So, is reductionism true? To be short, to my belief, yes. Professional philosophers and academics differ on this question and are liable to give you a very esoteric sounding explanation for whatever stance they take. I will try to explain my reasons for believing in reductionism as regards the reducibility of the mind to neurology, chemistry, and physics in as plain terms as possible. This will not be easy, so bear with me.
I’ve heard one objection to reductionism that goes as follows. Suppose you try to write a book about World War II, but not by using the ordinary language and explanations of psychological and economic motivations, but instead translate that story about the war into the language of physical and chemical processes in the brains of the participators of the war or the molecular and atomic movements in the muscles of the combatants. Would anyone even recognize that it was a book about World War II?4 Perhaps not, but I believe this objection to reductionism misses the point.
The point of reductionism in the theory of mind and psychology is not to translate the language of subjective experience into another language. The point is to explain what we subjectively experience in an objective, scientific way. (I espouse the theory of reductionism as explanation. I will not discuss reductionism as derivation or reductionism as translation. For a more technical and in-depth discussion of reductionism, I refer you to the Internet Encyclopedia of Philosophy article on reductionism athttp://www.iep.utm.edu/red-ism.) I may not recognize that a story describing a series of a vast multitude of molecular movements and reactions corresponds to a story of a man firing a gun, but I can certainly acknowledge that every action the body takes and every thought a person has is caused by physical and chemical changes in the brain. This has been demonstrated time and time again by the beautiful invention that is functional magnetic resonance imaging (fMRI). A working brain is a sufficient cause (and perhaps a necessary cause) of subjective thought. A working brain necessarily implies having subjective thoughts (in humans). It may someday be discovered that having subjective thoughts also necessarily implies having a working brain. (However, there are many people working on artificial intelligence that would like to think otherwise.) So, subjective thoughts can be explained by changes in the brain. As such, theories in psychology can be explained using theories in neurology, chemistry, and physics.
But, the skeptics may say, economics certainly cannot be reducible to neurology, chemistry, and physics. It’s a social science. How can you explain something as abstract as the money multiplier in terms of physical and chemical processes? My answer is this. Abstract ideas are instantiated by brains that recognize patterns. These patterns are mapped in the neuronal structure of the brain, and the brain recognizes these abstract ideas and forms new ideas by exercising these neuronal pathway patterns and forming new pathways in the brain. When someone thinks of the money multiplier, the brain’s neurons fire in a particular pattern unique to that individual. When he talks of the money multiplier and communicates his thought to someone else, his brain’s neurons fire in a particular pattern, and if the listener is familiar with the social convention known as the money multiplier, then her brain’s neurons will fire in the particular way that she has that abstract idea mapped in her brain. Likewise, all abstract ideas are instantiated and mapped in physical brains. This is where abstract ideas exist. Without brains there would be no abstract ideas. So, abstract ideas are reducible to neuronal pathway patterns which can be described in terms of molecular and atomic structure.
Furthermore, it is generally recognized in the neuroscientific community that processes in the brain operate according to sufficient causes. It is not widely agreed upon whether subjective thoughts play any causal role in the universe by themselves. So, given these scientific assumptions, viz. that the brain operates according to sufficient causes, and subjective thoughts distinct from the brain functions that they arise from don’t play a causal role, it becomes easier to recognize the need for reductionism of the human mind to the brain’s neurological, chemical, and physical processes in order to give a scientific explanation for the workings of the human mind. Without reductionism, we would have no scientific knowledge of the way the mind and brain work. On the other hand, with reductionism we have had tremendous progress in the study of the mind. Because of reductionism as explanation, we have had tremendous progress in understanding neuroscience, neurobiology, psychology, and psychiatry over the years. To put the argument in a valid form: (1) If reductionism were not true, then we wouldn’t have made any progress in neuroscience. (2) We have made progress in neuroscience. (3) Therefore, reductionism is true.
In conclusion, it appears that we are not free in the conventional sense. We cannot do other than what we do.