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Too few people know what they are talking about when they talk about determinism. Sometimes things said like « It is proved by experience that determinists are wrong : people are made by education. » or « Determinism is an outdated way of thinking », or even worse : « Determinism is an outdated way of thinking : it has been supplanted by chaos theory. ». So I'm gonna clarify some things that need to be.

Determinism is a philosophic idea according to which nothing happens at random. Just after comes the idea that a VERY precise cause will lead to a VERY precise effect, and as there is only one state of the universe at any point in time, then there is only one way for the following events to happen.

I Famous determinist philosophers : Laplace and Descartes

II Some prejudices about determinism

III Random ; unexpected criticism of quantum mechanics

IV Two interpretations of quantum mechanics

V The concept of Nomos


I Famous determinist philosophers : Laplace and Descartes

Descartes is officially the first to have extended the idea of determinism to the whole Universe, even though, being blinded by his Christian anthropocentric faith, he definitely wanted to think that humans had a soul that could work at random. Of course, every people prefer to think that they're free : determinism is incompatible with the existence of freedom because any act of any animal is determined by external and internal causes, causes that are themselves caused by very determined causes etc. But even with this small fault, Descartes was a true genius.


Descartes has impressively been able to predict the utility of science by its applications. For this and other things, he deserves to be forgiven for having been stupid enough to think that man is no animal.

When determinism is spoken about, it is often thought of as laplacian determinism. Laplace was a mathematician and physicist living in the nineteenth century. He has written in a letter that if a being gifted of a divine intelligence (“Laplace's demon”) knew the precise state of the Universe at a given moment, and all the laws that govern it, then it would be possible for this being to know everything in the Universe at any time, in the future as in the past. Why in the past, as the effect follows the cause ? Some explanation is needed. But as soon as you have understood, go to the next part.

When we consider a system that changes as long as time passes, its time changing parametres are always set by a differential equation. At least, that is what Laplace thought, and I think this idea is sensical. The solution of a differential equation is no number : it is a function. In this case, a function of a temporal variable because we consider that the other variables have disappeared with other equations. I won't give you the meticulous definition of a function. But “roughly” speaking, there is a type of input, a type of output, and the function is the link that associates to any input a single output. For example, “nose of” is a function from the set of animals that have a nose to the set of noses. With some patching up, it is possible to define the functions “intelligence of”, “twice of”, “father of”...

Well then, now, a nice diagram.


Autumn, a leaf on the river.

I have drawn in a graph different solutions of a given differential equation. Each line represents a solution ; in fact, the lines indefinitely extend to both the right and the left side, and between two lines, there is always another one, but which never crosses the others. To completely solve our differential equation, we need an “initial” condition of the system, that is knowing a specific input and the associated output (for example : at the start of the chronometre, the ball is at that place and has that speed). Once an IC is known, we know the function, then we know the output at any point in time ! The CI 1 point lays on a single line, and we can say that a line is the same thing as a function.

If Laplace's demon knows every equation and if it knows the IC of the Universe at a given point in time, then it knows everything.

Laplace's demon may lead to important paradoxes if it is part of the system, but I won't talk about this issue here.

II Some prejudices about determinism

Now, time for prejudices to be fought ! The following points give a better idea of what determinism is not :

-The idea according to which each individual is entirely determined by its genetic code : there is a word for that, but I have forgotten it. The extreme opposite, that cares too much about the environment, is called “behaviourism”.

-The fact that one day, man will be able to determine everything. Determinism means that things are absolutely determined, not that we humans can determine them in an absolute way. Laplace knew very well that his “demon” was an imaginary being : even the most powerful possible computer could not compute all that stuff, at least that's my opinion.

-Determinism does not encourage letting things happen badly. There are always relations of cause and effect, and even if our acts are determined by precise causes, they are also causes, then they may influence people and things around. Determinism is in no case a kind of fatalism that encourage to resignation, that is, submitting to injustice.

-Determinism does not imply that fights for freedom are in vain. Freedom does not exist, but there are feelings of pressure that are naturally bad for animals, just like humans. Being imprisoned in a small place, being forced to eat always the same thing, being forced to do something you don't wanna do... In fact, the issue is rather about feeling free, being blossomed. Oh, and for those who think that freedom is doing what you want : the more randomness there is, the more fate decides what you do instead of you.

III Random ; unexpected criticism of quantum mechanics

I am a determinist. I really think that there is no randomness, that “randomness” is just a fucking word used to create something that looks like an explanation, but that is none. But first, what does “random” mean ?

We are prone to imagine time as a straight line.


Ever learnt that at school ?

This is random :


Wow ! That makes the “Y” a great symbol !

There are several following ways of the time line. Each one can happen, each one has a non-zero probability.

Here comes an important question : if each one can happen, why would it be a specific one and not another ? Even having a very high probability does not make sure the thing will happen.

Illustrative interlude : extract of a particle physics lesson when I question the naive viewpoint of random. This is no caricature.


(Okay it's in French, maybe I'll make it in English, that would be even funnier ! ^^)

Oh fuck, I'm gonna do it, fed up. I'm gonna take the opportunity of that video to tell you what I think about quantum mechanics, because it is very close to the determinism issue.

What I hate the most in quantum mechanics, this is mainly quantum mechanicians. Most of them, acting just like unwise sheep, agree with the Copenhague interpretation of quantum mechanics : “There are freaky things we don't understand ? No need to wonder, go back to your calculation sheet. Electrons move randomly ? Of course, that's what I tell you. And if you don't agree, shut up, that's how it works. By the way, may I remind you that things are what they seem to be ? What do you mean, there are people that look nice whereas they are bad guys who wanna manipulate ? Sorry, you didn't knock at the right bandwidth of my ear. What do yo mean, it's my brain ? Blocked ? Darn, I don't understand what that kid means...”.

But there are some people that have suggested more suitable interpretations, and some of them are pretty modern. Here are following two of them that I know quite well.

Many-worlds interpretation :

Every way of the time line is taken and the different ways give birth to separate worlds.


Divergence of the time line

The problem of this interpretation is that it allows no prediction. We could imagine that these different time lines are part of a vector space with internal laws, but to know what those laws are, and even use them, I have no idea.

Overview of Einstein's interpretation :

Einstein, who definitely was an absolutist even though you could think he was not, has always been seeking... the most absolute interpretation. And also the least harebrained. Cause as seen before, there are harebrained interpretations. He has fought and debated a lot with Niels Bohr. Bohr was the spokesperson of the Copenhague interpretation, whereas Einstein was trying to defend the least harebrained viewpoints. The audience considered that Bohr was right at every point, but to me, he was right against Einstein at only some points.


The best physicist, all the more he was cool.


Einstein and Bohr discussing quantum mechanics. But if you know that Einstein was a pacifist whereas Bohr had taken part in the Manhattan project, that was aiming for building the atomic weapon for the US, you have some reason to think that these two men must have had more violent discussions...

Einstein is truly a character I admire. The so-called “principle of relativity” is merely an absolute point of view : the true laws of physics are always the same, even in a different referential. He has struggled like a wild boar against the new trend that wanted to think that random exists. Einstein said : “God doesn't play dice.”, then Bohr answered something like “Who are you to tell God what He has to do !”. All right, let's see another version of the same thing :

Bohr : God plays dice.

Einstein : Who are you to tell God what He has to do ?

Draw ? Nearly, but first, what did Einstein mean by “God”, he who didn't like catholiscism ? He meant “Nomos”.

V The concept of Nomos

In order to have a good idea of what Nomos is, it seems to me that a functional explanation is appropriate.

This is the graph of the square function from |R.


Gr x|->x²

The square function doesn't change. However, x² changes as x changes. Notice that this point can't be understood if you think “the function f(x)” like too many physicists do.

This is the graph of a function, here called g, that for a number a associates this number “times” the square function.


Gr a |->(x|->x²)

Here, the square function changes by a real factor ! But the function g remains the same.

Roughly speaking, I would say that everything changes except change. But I think it is better to adopt a functional way of thinking, and think that each change is governed by a constant upon it, more or less directly.

Nomos is the ultimate constant, the law that governs any other, then everything In fact, Nomos is what nature is made of. I believe in this because I don't believe in magic. Even in Harry Potter, spells don't work disorderly. Spinoza used the word “God” for Nomos. I think this is merely a computer program than a being capable of love or anger, just like, just like... just like humans.

In physics are studied the laws of nature. Physicists start with the idea that things don't happen in any way, because there are laws. Doing so, they nearly supposes that nature is a single law, that is Nomos' hypothesis. The ultimate goal of physics is to know Nomos : some physicists believe we only need to conciliate general relativity and quantum mechanics to make it, but in my opinion, this is a big illusion. We may never do it.

Notice that the many-worlds interpretation has just been created to conciliate the Nomos' hypothesis with the existence of a kind of random.

Conclusion :

But now, I would like us to come back to some common sense. How to prove that randomness exists ? You can always imagine that we have forgotten something : a mathematical tool that could be useful to make the problem more simple to be discussed, an unknown parametre... After all, humans are not transcendent, there will necessarily be things that our intelligence and senses cannot reach. There are things that we can't know. But how could we know that we can't know them ?

Finally, I have an ultimate argument to assert that the determinist approach is the best : it leads scientists to search, because they think there is a law, and it leads nice people to act in order to make a better world, because they know their action is not in vain. Well, what are we waiting for ?

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