The Nature Of Consciousness


Question: What is the fundamental principle by which the brain operates?
Answer: Computation.

Don't worry if you didn't get the right answer. Very few people probably realize this and most people probably will refuse to believe it, even though it's scientific fact.

Question: What, in addition to computation, gives you your consciousness?
Answer: We're not completely sure, but my hypothesis is that nothing extra is needed.

Most people will answer that some kind of additional magic pixie dust is needed, because their conscious experience feels just oh so special. This magic pixie dust (MPD) may be a supernatural soul, the will of God, quantum mechanics, the Flying Spaghetti Monster, or any number of other silly or non-applicable concepts.

My hypothesis is that the meat in your head is all that there is. The enormous complexity of the brain is sufficient to explain all of our cognative abilities and our consciousness is easily explained as being just a useful illusion. There is no afterlife; when you die, the computational process in your brain ceases and so does your conscious experience. This view of reality is called the computational theory of mind.

I call this position a “scientific hypothesis” because science will eventually have the power to confirm or refute it. If it is confirmed in a few hundred years, we will have a re-run of the Evolution vs. Creationism controversy, as the Catholic church, among others, has declared a supernatural soul to be a fundamental tenant of its belief system.

The following is still being edited.

Digital Logic Gates


Digital Circuits

Most people won't have a solid concept of what “computation” is or how it is realized. As an example, assume that we wish to compute the sum of three integers, each between zero and one (i.e., binary digits). The computer-hardware circuit to do this is called a “Full Adder”. Here is a circuit diagram [from Burnett 2006]:

[Full-Adder Circiut Diagram]

The three input digits are "A", "B", and "Cin", where a value of 1 is represented by electrical current and 0 by no current. The output is two binary digits, with "Cout" as the most significant and "S" as the least. I.e., Cout=0 and S=0 means the sum is 0; 0,1 means 1; 1,0 means 2; and 1,1 means 3. The lines and dots in the diagram are links and connections and the shapes the links go to and come from are different kinds of logic gates.

Logic gates perform even simpler computations than the full-adder circuit and are built from transistors on silicon chips in modern computers. Transistors function by using the odd electrical properties of silicon, which itself is a chemical element. The contemporary Intel Core 2 Duo processor has 820-million transistors in it that form logic gates that form simple circuits that form even more abstract computation structures, which are ultimately controlled by software that is devised by people.

You can ask the philosophical question of whether the full-adder circuit has any “concept” of what it is doing. Quite clearly not, since it doesn't need any “intelligence” to perform its function; it's just an electrical function, not fundamentally dissimilar to a copper wire conducting a current. Does the wire “know” what it's doing? Only in the sense that the forces of nature always seem to “know” what to do. No magic pixie dust is required to explain the operation of a full adder or a computer processor chip or your favorite software program.


In the brain, the basic computational element is the neuron. It is conceptually analogous to the digital logic gate, though it functions a bit differently. The neuron is an electro-chemical device that takes a number of analog inputs from other neurons and “fires” when the accumulated electrical level of all inputs reaches a particular threshold level. A firing is an electrical output pulse that goes to the inputs of all other neurons the neuron in question is connected to. After firing, the neuron's internal level is reset to zero and the process begins again. A neuron that is being heavily stimulated at its inputs will not output a greater signal level when firing but it will fire more often.

The interface points where neurons connect to other neurons are called synapses. The connections can have differing “weights” that carry differing levels of signal from the input neurons. The weights can even be negative, causing an inhibitory action. Well, this is the simple model; real biological neurons are more varied and complex, but the important thing is that they operate in this fundamental mechanical way. It should be obvious that an individual neuron has no more “understanding” or “consciousness” than a digital logic gate.

Neural Networks

The real power of neurons is realized when you connect lots and lots of them together in a neural network.

In a neural network, the hardware is the software.


The Human Brain

The contemporary adult human brain has around 100-billion neurons and 3-quadrillion (thousand trillion) synapses; i.e., each neuron has an average of 30,000 synapses.

A 16-GB flash memory chip has over 128-billion transistors in it, larger than the number of neurons in the human brain. Does it have a consciousness?

DNA and brain development.


The Useful Illusion

Why do we have a consciousness at all?

Do animals have a consciousness (billions of neurons)? Does a C. elegans worm (308 neurons)? Does a bacterium (0 neurons)?

No Escape

If you ask a person if they are sane, should you believe their answer? The only means you have to evaluate the experience of your own consciousness is your own consciousness itself. If your consciousness wasn't some supernatural thing but instead was a little program in your brain to fool you into protecting your existence above all else by creating the illusion of being something special and supernatural, you wouldn't be able to tell the difference.

Not only is there a reason for me to believe that my own consciousness exists, but (according to Descartes) it is the only thing I can be certain exists.

However, you are a faulty witness to your own consciousness.

Religious people like to quote the Bible for “divine revelation”. I like to quote Futurama. Consider the following sacred passage from Futurama 1:01:

Fry: You're a bender, right? We can get outta here if you just bend the bars!
Bender: Dream on, skin tube. I'm only programmed to bend for constructive purposes. What do I look like, a de-bender?
Fry: Who cares what you're programmed for! If someone programmed you to jump off a bridge, would you do it?
Bender: I'll have to check my program. (short pause) Yep!

Like Bender, you may simply be unable to escape from your own programming. Fortunately, Bender's programming was altered by electrocution shortly thereafter, but your programming is still intact.

Magic Pixie Dust

Quantum Mechanics

Quantium Mechanics is often trotted out by scientifically knowledgeable people to explain consciousness. They reason that Quantum Mechanics is mysterious and consicousness is also mysterious; therefore, the two go together. It is also a comforting thought that the ‘randomness’ of Quantum Mechanics means that we are not deterministic robots in a clockwork universe.

The trouble is that Quantum Mechanics doesn't fit in with neuroscience. Quantium effects influence events at the sub-atomic scale, whereas individual neurons are gigantic in comparison, and neural processes involve the interaction of billions of neurons. If Quantum Mechanics has any influence over thought processes, it is like butterfly wings affecting global weather patterns, an infinitesimally small contribution. But really, any Quantum effects would be noise to the brain's signals that the brain actively filters out.

Future Experiments

Not-So-Free Will

Philosophical Gibberish

You've got to love philosophy. These guys will conjure up some definitions, argue about them for centuries, and not produce any useful answers. If only I could get paid for doing this.

Parallels to Creationism

The Bible says something. The Church interprets it a certain way. Science disproves the way the Church interprets it. The Church goes to war with Science for a century or two and loses. The Church concedes defeat, though some embarrassing followers never give up. Lather, rinse, repeat.

If They Were Alive Today

If Rene Descartes were alive today, he would probably say “I am; therefore, I think”. A counterargument often used against the computational theory of mind is that really intelligent guys from a long time ago believed otherwise. Of course, these guys also believed things that we know today are objectively false. The fact is that if these guys knew in their time what we know about reality today, their positions probably would have been markedly different. They openly admit they stood on the shoulders of giants to see further, but these guys didn't have any giants' shoulders to stand on for this subject.


The brain is a computer. Your consciousness is most likely a computational processing running a program that fools you into protecting your own existence. It's also a handy executive abstraction for high-level strategies unencumbered by the massive low-level processing of vision, memory, language, etc. A digital computer would do the same thing if it had hardware and software as sophisticated as and of a similar form to the brain.

The issue is a lot like religion and science. Science is able to explain the development of the universe and living creatures, but religious people insist that the real answer is science *PLUS* "magic", where the "magic" part is completely superfluous and extraneous to all of existence. Similarly, the circuitry of the brain is entirely able to explain our capacities and experiences, but most people will insist that the real answer is the brain *PLUS* some kind of supernatural "magic" which is completely superfluous and extraneous to the functioning of the brain.

The "magic" part is also more complicated than the object being explained; with the brain, it is a homunculus argument. Imagine that you press the square-root button on a calculator. To give you the answer, it doesn't press the square-root button on another, smaller calculator inside of itself; it computes the answer using its circuitry. This power might seem miraculous to someone who doesn't understand how software and logic gates work.

You can witness the lack of a "soul" in the way that drugs and brain damage can completely change a person's personality. If it's your "soul" that's in charge, how can this happen? Your "soul" is, completely coincidentally, exactly of the form of the consciousness that you are experiencing right now, so how can it change? If you suffer brain damage, will your "soul" be restored in the after life to what it was before the brain damage? Will you take all of your memories with you to the afterlife? Your memories will be "left behind" in a rotting lump of meat. If the "soul" is what many people seem to think it is, why do we need all of the neural circuitry found in the brain? Our brain should be a bag full of blue smoke.

The above is a scientific hypothesis that we will one day be able to test if our technological capability keeps increasing. We will be able to map every neuron and synapse of a person's brain and recreate it in a digital-computer simulation. Then we fire it up and see if we get a "person" who thinks he is "conscious". We will also be able to monitor the consciousness process neuron-by-neuron and manipulate it directly. We may discover, again, that we're not quite so special after all.

Now consider everything that we know about reality. Does the universe work more like a precise machine or more like some transcendental mystical metaphysical drug hallucination? Consider everything we know about the mechanics of the brain. It is organized a lot like and its components are a lot like a computer. Is this a description of a ghost trap or of a computational device?

The Earth sure does look flat, though, doesn't it?

Most people seem to believe that their consciousness demonstrates that they are special and have a supernatural soul that will have an afterlife. However, there's no good reason to believe this.

The block diagram for the "it's an illusion" theory of consciousness doesn't have a big box in the middle of it labelled "Magic happens here". All other theories of consciousness do. This gives it more credibility than other theories of consciousness.

Computers are pretty remarkable, too. They can do all sorts of cool things. Suppose that we could program a computer to believe that it was experiencing consciousness. This would be an especially remarkable thing. However, would its consciousness be something 'real', some new part of reality, or would it simply be a computational process in-flight like your web browser is now?

Descartes was a smart guy, but he didn't know what we know today. Would he have a different opinion today?


Copyright © 2008 Dr. Craig S. Bruce, Ph.D.

I, the copyright holder of this work, hereby publish it under the following license: Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".

[Burnett 2006] Full-adder circuit diagram copied from Wikipedia, copyright © 2006 by Colin M.L. Burnett, reused under GNU Free Documentation License.

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