When I say totally random, I mean absolutely random, not pseudorandom.

If I want to say "totally random" numbers such as 1,26,17,4,1 and 27, although I see them to be totally random, they aren't. These are numbers that I think are influenced by my childhood, ideology and everything that I've seen.

So, what do you think? Is there anything completely random?

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    This questions seems to be a duplicate of Are humans capable of generating a random number? – Outlier Mar 21 '12 at 23:22
  • could you please elaborate what you mean by universe? In my answer also, I stated that I don't really know how the universe is relevant to your question. Is there any chance you could expand on your question? – Outlier Mar 21 '12 at 23:46
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    The answer simply depends on how you define "Random". In a very liberal sense, random is just something that is unpredictable. A fair coin toss, then, is sufficiently random. The problem comes in when you try to apply a more strict definition of random; perhaps an event is truly random when the probability of the possible outcomes is equal. But in a deterministic universe (and much of what we see in our universe very much appears deterministic, even if it isn't "underneath"), there is only ever one possible outcome to an event. So randomness defined in this way doesn't even make sense. – stoicfury Mar 22 '12 at 0:11
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    Also, this question on randomness, determinism, and free-will you might find interesting. – stoicfury Mar 22 '12 at 0:33
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    Nothing in Nature is random. A thing appears random only through the incompleteness of our knowledge (Spinoza). – robin girard Mar 30 '12 at 11:04

15 Answers 15


To answer your question, or at least get at some sort of picture, let's consider the following. What is random? Hmmm. Without getting into the details of the matter, or philosophical implications, we may define "random" in a very intuitive manner as this will mostly do for a discussion of this scope. Let us then propose that an event which is "completely" random is one for which it is logically (or formally, i.e. in the sense of mathematical rigor) impossible to associate any rule, pattern, or reason. This is, of course, where it all gets tricky.

In the way "random" has now been defined, it may be possible to generate an event, at least cognitively, which would be viewable as truly random. To take your example a bit furhter, let us conduct a thought experiment. Imagine we're walking down a busy city street. We decide to ask every person that passes by, and decides to stop and give us five seconds of their time, to pick a number. By this, we may construct two sets. Let set X denote the numbers we record, in the order we encountered them; and let Y denote the set of indicies of the people who stopped and gave us a number. So, for example, if the third, seventh, and twelfth person we asked stopped and gave us a number, Y = {3, 7, 12}. Certainly, the sets X and Y may not be random in the sense that we have defined.

But, then we may ask the question why the sets have the particular pattern or rule associated with it. Could there not have been different sets? And so, by our criterion for true randomness, the reason the sets X and Y are what they are, is random. I can't come up with the proof for the criterion off-hand, but I suspect Goedl's theorem's in there somewhere.

It is worth noting that by our definition, it may be the case that no event which occurs in nature could be viewed as random. So, that may answer your question about there being anything truly random in the universe. On the other hand, we may very easily have events that qualify as truly random as long as they exist in some "virtual" reality as the one discussed in the example above. But, it's truly an understatement when I say that that's a topic to be discussed another time.


Quantum mechanical processes, such as a circularly polarized photon striking a surface that is linearly polarized (whereupon it, to anthropomorphize the situation, has to choose whether it was really polarized perpendicular to or parallel to the polarization axis), do not appear to be (locally) deterministic. For all practical purposes, therefore, it makes sense to consider them as "completely" random. It is formally possible that there are hidden state variables distributed throughout the universe away from the photon itself that nonetheless govern its behavior, but since no-one has figured out a way to test those, living in such a universe and living in a genuinely nondeterministic one may be indistinguishable.

(See "Bell's inequality" for more details.)

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    @stoicfury - Yeah, I had a similar thought ("How many times have I posted this on SE.Philosophy now?") – Rex Kerr Mar 22 '12 at 16:41
  • I thought there was some decisive proof against the possibility of a consistent hidden-variable system? On the other hand -- isn't the wavefunction entirely deterministic (except of course when it collapses; but how to interpret its collapse physically being a matter of significant debate)? Just some lingering questions; great answer and +1. – Joseph Weissman Jan 13 '13 at 19:07
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    @JosephWeissman - It is deterministic in that it deterministically specifies a mathematical object that can, among other things, be used to calculate a probability distribution from which events seem to be drawn (i.e. it matches that distribution). So it's deterministically random, in a sense. Also, the decisive proof is only against local hidden variables--that's the Bell's inequality thing. Nonlocal variables cannot be ruled out: "Russel's teapot contains a cryptographic-quality random number generator used to pick from every distribution, rendering everything strictly deterministic." – Rex Kerr Jan 13 '13 at 22:36

Although this question is very closely related to the one which I commented about, I will still give an answer because the question is asking for a different answer.

Before I give you an answer, I want to clear one thing up.

I don't quite understand what you are trying to convey when you state

Is there anything completely random in the universe?

This question seems quite incorrect as numbers are a theoretical concept invented/discovered (either which are open to debate: the question with the highest votes on this site) by human beings and are (as far as our knowledge concerns) exclusive to humans and the creations of humans (e.g. computers).

Therefore, I don't understand what you mean by "the universe".

First of all, it can be debated whether humans can/cannot generate random numbers. However, for the sake of simplicity, let's pretend that humans, cannot under any circumstances generate random numbers.

That does not mean that it cannot be generated at all:

Computers are a prime example of something that can generate the closest thing to a truly random number. They are senseless, unbiased, and are not conscious. Thus, past experiences don't affect them at all (unless otherwise programmed). They are linear machines that perform only the tasks they are instructed to, no more, no less.

EDIT: In response to Stoicfury's comment, I am adding more to my answer.

Apparently, eventually, even computer hardware that can generate numbers that are very close to truly random, after a while, a rough pattern can be detected.

In that case, the closest thing you will ever get to creating a truly number generator is on random.org where the determined number is based on the slightest deviations in sound in the atmosphere. In this case, however, this randomness is no longer computer generated but rather generated by the environment.

It depends what you define as random, really.

If you define it to be a number that is generated unbiased and at the same time independent and uninfluenced by any physical factors, then it is impossible due the law of cause and effect.

  • But computers need to be programmed. And the programmer who wrote the program to generate that you name "random numbers" knows the algorithm to generate them. So, it could calculate them with a piece of paper and a pencil. – Garmen1778 Mar 21 '12 at 23:52
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    No, that's not how it is. Wikipedia states: "In computing, a hardware random number generator is an apparatus that generates random numbers from a physical process. Such devices are often based on microscopic phenomena that generate a low-level, statistically random "noise" signal, such as thermal noise or the photoelectric effect or other quantum phenomena. These processes are, in theory, completely unpredictable." See this page. – Outlier Mar 21 '12 at 23:55
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    :( It's actually well known that computers (software) have a hard time generating completely random numbers (where random = essentially entirely unpredictable). If you record the random numbers generated by an computer eventually you'll see a pattern. See also here. Using additional hardware like measuring radioactive decay or something makes it a lot more random, but I would argue it's still not wholly random. In a deterministic universe, true randomness doesn't make any sense. – stoicfury Mar 22 '12 at 0:00
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    @Outlier: Exactly. The last sentence you write is key. Random means unpredictable, but if everything has a cause, nothing can be inherently unpredictable (because you could just learn more about the causes and thus be able to predict the outcome). Closest you can get is probably through quantum mechanics. – stoicfury Mar 22 '12 at 0:27
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    @stoicfury your logic now makes perfect sense. Completely agreed. – Outlier Mar 22 '12 at 0:50

The answer simply depends on how you define "Random". In a very liberal sense, random is just something that is unpredictable. A fair coin toss, then, is sufficiently random. The problem comes in when you try to apply a more strict definition of random; perhaps an event is truly random when the probability of the possible outcomes is equal. But in a deterministic universe (and much of what we see in our universe very much appears deterministic, even if it isn't "underneath"), there is only ever one possible outcome to an event. So randomness defined in this way doesn't even make sense.

If you want to address existing empirical evidence of what science might call "randomness" in our seemingly deterministic universe, Rex Kerr provides the best answer for that. Please upvote him accordingly:

Quantum mechanical processes, such as a circularly polarized photon striking a surface that is linearly polarized (whereupon it, to anthropomorphize the situation, has to choose whether it was really polarized perpendicular to or parallel to the polarization axis), do not appear to be (locally) deterministic. For all practical purposes, therefore, it makes sense to consider them as "completely" random. It is formally possible that there are hidden state variables distributed throughout the universe away from the photon itself that nonetheless govern its behavior, but since no-one has figured out a way to test those, living in such a universe and living in a genuinely nondeterministic one may be indistinguishable.

(See "Bell's inequality" for more details.)

See also: What is the difference between free-will and randomness and or non-determinism?

  • Says a totally random comment turned into answer. :P – cregox Apr 24 '14 at 20:10

If you duplicate a conscious observer in a classical universe, copy an artificial intelligence to two big computers, or make a cell-by-cell duplicate of a sleeping person, the way the consciousness goes subjectively is completely random. There is no way (from the inside) to know which way your feeling will end up going.

This is important, because it is philosophically how the many-worlds interpretation of quantum mechanics explains the randomness in quantum mechanics. But it does not require quantum mechanics to duplicate an observer--- you can do it any way you like, and the result is random subjectively, meaning that there is no information that you can get ahead of time that tells you which copy you will be, because you are going to be both.

EDIT: Clearer explanation

Suppose the transporter on the Starship Enterprise is malfunctioning, and you're Captain Kirk, and you want to beam down to the planet surface. The transporter makes a million copies of Kirk, and leaves them at different places on the planet, each one is identical.

The question that is asked here is which Kirk will you "feel" yourself to be after the event has happened? You can determine this afterwards by introspection--- you just look around to see where you are. But the information regarding which one you are going to be is purely undeterminable to you in advance as Kirk, and you can, at best, post probabilities.

The nature of these probabilities are fundamental--- but they are subjective. Someone else will know exactly what's going on--- duplicated Kirks. But duplicated Kirk's mean that your perception is splitting between many entities, so that, since you must choose one path to take, your path is entirely random.

This idea is derived from Everett's many-worlds interpretation of quantum mechanics in 1957, but this type of thing also appears much later in the popular philosophy literature by Dennett and Hofstadter in "The Mind's I", and it is echoed in 1980s philosophy by many people. It does not appear before Everett in any form.

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    It's irrelevant — if they are all really identical copies, it doesn't matter whose cells are the "original" and whose are the "copy" because they would be indistinguishable. As soon as Kirk is dematerialized, that instance of Kirk ceases to exist. When Kirk is rematerialized, every rematerialized Kirk will be a new instance of the original Kirk; None are the "original". They will all feel like the original Kirk. – stoicfury Mar 29 '12 at 17:47
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    Hmm, you seem to be missing the point... If you are Kirk and you want to know where you'll end up, it's quite easy: no where, because you'll be dead, or "dematerialized" or however it's done. I see no mystery in that. There's no randomness, no variables, no math; the entirety of your being simply ceases to exist, and the copies of you — which think and feel exactly as you do but are not you — are created elsewhere. – stoicfury Mar 31 '12 at 15:22
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    @stoicfury: you miss the point--- you are constantly changing, new cells for old. Are you constantly dying? There is no continuity of matter required for continuity of experience--- you can replace one cell for another and keep the experience the same. If you do this for the whole brain, and duplicate the cells in the process you will have experience continue into two brains from one, and which brains "you" will feel to be in will not be determined. You can read more about it in "The Mind's I" by Hofstadter and Dennett, but it is contained in the many-worlds intepretation of Quantum Mechanics. – Ron Maimon Apr 1 '12 at 8:45
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    How do you deal with the no-cloning theorem? – labreuer Oct 20 '13 at 6:48
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    Do we really know enough one way or the other to know whether a person's quantum state (not just classical state) is important to what constitutes him/her? So little is known about consciousness that your stance seems to be 'jumping the gun', as it were. – labreuer Dec 4 '13 at 17:41

The thing itself is never random. The thing itself merely is what it is.

Thus instead of looking for a random thing, we want to find a process that produces things randomly. Many believe that quantum mechanics yields truly random results. This means that it follows a probability distribution. But if quantum mechanics is superseded by a determinist theory, then this goes out the window. Thus even here randomness is more a story for observation than an absolute necessity.

It is true that most processes we see as random are actually strictly determined by forces. We simply don't have the information to determine the forces. For instance, a penny flip is something we treat as random, whereas we really just lack information as to how we flipped the coin.

  • I think your last paragraph is definitely true. Much of what we call "random" in many contexts is just something that has insufficient information for us to predict. But I wonder about the accuracy of your first two claims. Specifically, your argument seems to be that something we presently think is random can be superseded by a later understanding of the thing as determined. But this seems inadequate as proof, because it hinges on a sense of possibility that either hides a prior commitment to determinism or is possible the same way it's possible for me to wake up as a frog tomorrow. – virmaior May 8 '15 at 5:19
  • I agree it is no proof (whatever that proof would mean) However the universe admits a deterministic theory. It just might be too elaborate/ arbitrary/ useless for people to discover. Take for instance the theory that merely is union of all the states of the universe. – Jacob Wakem May 8 '15 at 15:15
  • Two things confuse me in your comment. (1) By "admits", do you mean allows? (2) your last sentence seems to involve equivocation on the meaning of the word theory insofar as yes you could have a "theory" that is merely the aggregate of all the states of the universe, but such a "theory" explains nothing insofar it provides no model or simplification (since it only replicates every point). But neither of those helps with the bald claim that the universe is simply deterministic. – virmaior May 8 '15 at 15:31
  • @virmaior: What he probably means is that the universe could have been set up to run deterministically through all the states it is going through, all of which were fixed in advance (outside of spacetime), just like a movie plays deterministically through all its frames. This shows that we cannot totally reject the possibility of a deterministic theory, though we certainly should reject the 'movie' theory because it has the same complexity as the data (which exactly as you say provides no simplification). – user21820 May 24 '16 at 2:53
  • Your 1st paragraph (one line) is a tautology. Adding it obfuscates & adds nothing to the discussion. | Your 2nd paragraph is founded on your " ... if quantum mechanics is superseded by a determinist theory ... " -> which has been sought ever since QM was postulated, so far with no success. It MAY be that QM will be essentially "disproven" - but it's as likely to be when the flying pigs bring green cheese from the moon as any other time. | Your 3rd paragraph is essentially orthogonal to what is being asked, even if it were not falsified by QM, as it is for this discussion. – Russell McMahon Oct 24 '16 at 6:44

Random does not mean uncaused. It simply means the chain of causality between events are unrelated. If a password is generated where each character is determined from a common source using the same algorithm then they are only pseudo-random because the sequence appears random but the characters are causally related. It's insecure because at least in theory some information about one character could be determined from another. If each character were drawn from a different source and/or using a different method then it would be random, and knowing one character wouldn't reveal information about another. They'd be causally separate.

  • In classical probability theory, we can have a single probability distribution from which we can draw multiple samples, each being iid random variables. Likewise it's conceivable that there may be a single physical process that produces random bits. White noise is often taken to be essentially truly random. Furthermore, just because two random variables are correlated does not imply that they are not random! Of course, whether or not true random processes exist is unclear, which is the actual question. Finally, lack of causal relation does not imply randomness! – user21820 May 24 '16 at 8:42
  • There's a difference between things that appear or are treated as random in probability theory and actual randomness. A single physical process I think could only be convincingly pseudo-random. You're correct it's possible for unrelated processes to be correlated, but that doesn't mean it's not random. The question wasn't whether any process is random, it's whether anything is random. I think I answered that. – Tanath May 24 '16 at 17:14
  • I don't think you understood the point I was making, so let me clarify. You say that "random" implies "causally unrelated". That's false even for true randomness. Why? Suppose I actually have a source of true randomness and I obtain a random bit x from it. Then I set y to be the negation of x. Clearly y is directly causally related to x, but both x and y are individually truly random though each is completely determined by the other. Thus you cannot use any causal relation to infer anything about true randomness. – user21820 May 25 '16 at 2:33
  • Secondly, you implicitly affirm the reverse implication as well, namely that "causally unrelated" implies "truly random". That too is obviously false. Thirdly, if you want to make the claim that any physical process can only produce pseudo-randomness, then it's a different claim and requires justification. I'm not saying I disagree with it, but your answer did not state it nor give any justification for it. – user21820 May 25 '16 at 2:39
  • Seems you're looking at randomness differently so you interpret my answer differently. I rejected your premise (you have a source of true randomness), though I'm not sure how committed I am to that position. It's a single source and so information about 1 bit could give information about other bits. In your example y wouldn't be random as I've described. It'd be equally unpredictable if you had no info about x, but info about one would give info about the other so can't be used together to produce random sequences. You say it's obviously false that causally unrelated implies truly random. How? – Tanath May 26 '16 at 17:10

"Is there anything completely random?" could be interpreted to mean: "Is there any agent that does not work toward a determinate end?" In other words: "Is there a being without a final cause?"

Cf. Oderberg's open access (free) 10 March 2016 The Monist article "Finality revived: powers and intentionality."

  1. "Being" requires "oneness" (unity).

    cf. St. Thomas Aquinas's commentary on Aristotle's Metaphysics book X, lesson 3 ("The Nature of Unity"), #1974-1977:
    1974. That unity and being[etc.…, a reference to what Aristotle says at #](832).

    Since he [Aristotle] had given the same argument for being and for unity, he now shows that unity and being somehow signify the same thing. He says “somehow” because unity and being are the same in their subject and differ only in meaning. For unity adds to being the note of undividedness, because what is one is said to be an indivisible or undivided being. He gives three reasons why unity signifies the same thing as being.

    1975. (1) The first is that unity naturally belongs to all of the different categories and not just to one of them; that is, it does not pertain just to substance or to quantity or to any other category. The same thing is also true of being.

    1976. (2) The second reason is that, when a man is said to be one, the term one does not express a different nature from man, just as being does not express a different nature from the ten categories; for, if it did express a different nature, an infinite regress would necessarily result, since that nature too would be said to be one and a being. And if being were to express a nature different from these things, an infinite regress would also follow; but if not, then the conclusion of this argument must be the same as that of the first one.

    1977. (3) The third reason is that everything is said to be one inasmuch as it is a being. Hence when a thing is dissolved it is reduced to non-being.
  2. A completely random being cannot be one.
    Primary matter (cf. De Principiis Naturæ) is pure chaos, formlessness; form united with primary matter is what makes something an actual being.
  3. ∴, a completely random being cannot be a being.

Thus, there is not "anything [any being] that is totally random".

  • Can you expand on this? I get what you're saying but it will obscure to anyone who has not studied Aristotle and/or Thomism – virmaior Feb 22 '16 at 21:45
  • @virmaior See the quote I added to my answer. – Geremia Feb 24 '16 at 3:39
  • Downvoter, could you please comment why you down-voted? – Geremia Apr 28 '16 at 23:09
  • I downvoted because it's not answering the question, which is not about true chaos (completely no order), but about true randomness. Since the asker explicitly mentioned the distinction between true randomness and pseudo-randomness, we can be certain that he's not asking about true chaos. If he was, then I agree with your answer that there's no such thing as true chaos. This has implications for example in questions like "What gave rise to the Big Bang?" It cannot be true chaos, regardless of whether we can understand it. – user21820 May 24 '16 at 2:46
  • Sorry I'm still not convinced your answer has any bearing to the question. Unless you assert that true randomness cannot occur because it would somehow require true chaos, this is simply not relevant. If you disagree, tell me why and I'll gladly reconsider. – user21820 May 24 '16 at 8:33

According to hard determinists, true randomness doesn't exist (not even at the quantum level) and everything in the universe behaves exactly as predetermined since the Big Bang.

Others would argue that quantum physics and/or free will are inherently nondeterministic. While I don't think there is any evidence for this whatsoever, I guess this perspective remains popular because most humans don't feel comfortable embracing the notion that they're essentially just bio-chemical robots and that every thought and feeling they have is predetermined since the Big Bang.

Anyway, I would recommend Introduction to Randomness and Random Numbers by Dr Mads Haahr for an introduction to randomness, Pseudo-Random Number Generators (PRNGs), True Random Number Generators (TRNGs), the difference between both as well as the very nature of randomness.

  • And how are the hard determinists going to answer the question of whether or not the Big Bang itself was a random event? If it was predetermined, then predetermined by what? A commonly offered explanation is that there is a closed loop in spacetime, but it is utterly ridiculous because without the Big Bang there is no spacetime. A quantum foam, someone suggests? What in the universe is a quantum foam? And what determines the characteristics of this foam? – user21820 May 27 '16 at 4:41
  • @user21820 : There is some disagreement on whether the Big Bang was in fact the beginning of all existence. There's not even agreement on whether it actually occurred. A new model in quantum physics confirms pre-scientific notions that the universe is eternal and has neither beginning nor end. As you pointed out yourself, a closed loop in spacetime would solve the issue. – John Slegers May 27 '16 at 7:32
  • I didn't say it solves the issue!!! In fact it's just another silly turtle. Whether or not there is a Big Bang (in the conventional sense), using a closed spacetime loop to explain the universe is no better than using God, because now what is the underlying framework that supports the existence of the loop? How did the loop exist in the first place? You can't have something from absolutely nothing. It doesn't matter how many people come up with new-fangled theories. No experimentally testable prediction? No go. – user21820 May 27 '16 at 7:36
  • @user21820 : Just assuming the existence of a God because you can't some up with a better explanation is irrational and pointless. Maybe the universe created itself. Maybe something external created itself. Maybe the universe needs no creator. Whichever of these is true, it science can't answer it it's essentially unanswerable. – John Slegers May 27 '16 at 7:43
  • That is what exactly you are doing. And that is my point. Just assuming the existence of a closed spacetime loop because you can't come up with a better explanation is irrational, pointless, and worse still, dangerous because it is used to lie to people in the name of science. You are right that such questions are unanswerable by science. That's my point too! So you shouldn't have cited some so-called science article. – user21820 May 27 '16 at 7:46

Everything in this world is interconnected.

There are no accidents.

Any connection between any given set of beings/things that one does not understand is termed as random by him.

Thus, in simple words, No. Nothing is completely random. however, the most random thing in the universe would be dependent on the person who is asking the question

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    I'm sorry to be so blunt, but there is one large complaint to this answer: [citation needed]. Please elaborate on your statements and reference them to establish credibility; it's hard to trust an answer with so little explanation and sources. – commando Mar 29 '12 at 18:57
  • I will work on that but if you are talking about logic, its all there in the answer. Please ask if you don't understand something in my answer – MozenRath Mar 29 '12 at 19:01
  • I was talking about "everything in this world is interconnected" and "there are no accidents." Sure, this may be true, but I would like sources that affirm that. – commando Mar 29 '12 at 19:10
  • I'm not really concerned about sources so much as some known concept your idea is drawing from which we can reference. Most answers won't require direct citations if they use well-established concepts in philosophy along with recognized forms of reasoning (i.e. classic logical deduction). I look through answers for keywords, like determinism or qualia or an author's name and this gives context clues to what the answerer is referring to. But here it's not clear if this is your own (unsupported) opinion or some ancient philosophy I should know about (that may be very supported)... :-) – stoicfury Mar 29 '12 at 19:47
  • Although I have reservations about your first statement, I definitely disagree with your second statement. "Accidents" are happening all the time, and every where! Also, there are many things I don't understand, but I don't tem them as random. – Guill Oct 24 '16 at 21:32

I would reduce the idea down and classify it into two types of randomness. One: necessary and the other: contingent. The opposite would be 'order' and likewise, would also maintain necessary and contingent attributes.

Natural randomness and order are both necessary. Our internal impressions of them are contingent. That is, relative to our own special place and moment in time.

One might reduce the Natural phenomenons further to potential, quantum probabilities, or retro-causality verses real-time, real-world causality. Who knows.


You are intermixing two things:

  • something is random or not
  • the distribution of something, which might be equal or not¹

¹) very often, it isn't an equal distribution, but a normal distribution, when most cases are grouped around an average. Think: body size of persons of same age and culture: Most are around 1.8m, fewer 1.7m or 1.9m, far fewer 1.6 or 2.m. But rarely two childs from the same parents are of exactly the same length.

If you enter a casino, you will hardly find anybody who can predict the next card from the deck, or the next roulette number. Some might believe they know a way to predict it, but they can't.

Some people here might think, that if they knew enough parameters, they could predict the next roulette number, but think of it! The microscopic shape of the billiard ball will change with the temperature, and you can't shield a Casino from the outside world, to prevent any influence. The air is moved by the breathing of the visitors, and you can't calculate when whom of them will breath - it's not a problem which will be solved in 100 years with more computer power. It is systematic: The finer conditions of roulette are uncontrolled.

So the outcome is random.

My first impulse was, to write "true random", but as serious adults, we always tell the truth, of course, so if we say random, we mean random.

You might construct a roulette canon in a laboratory, which generates predictable results, but you will not get a license for that. That much is predictable too. :)

Now to the second, related questions. Some people believe that only equal distributions, like from throwing a dice, are random. But that's not the case.

Consider a bowl with two black and one white ball, and you pull blindly from the bowl and put it back each time. You will pull a black ball with 2/3 chance and a white one with 1/3 chance. It is not predictable which color you will get, but the probability is not equal - it is 2:1.

But knowing that, you could transform it into an equal distribution: If you pull a white, it is white, but if you pull a black, you have to pull a second black one. Generated by a PRNG:

w, b, b, w, b, w, w, b, b, b, b, b, b, b, b, b, w, b, b, b, w...
W     B  W     W  W     B     B     B     B     W     B 

Here we see a 5:6 relation, which is of course no proof, but the proof is more a case for Mathematics.SE or Statistics.SE. It's only to show how it works. Now: If you know the bias of any random distribution, you can transform it into an equal distribution, which means, that an equal distribution isn't such a magical thing. You could for example measure red and non-red cars which appear on the other side. If you counted a lot of them, and know the distribution, you can correct the unequalness by calculation.

People with a deterministic viewpoint might argue, that, given enough data and big machines, and knowing all natural laws in greatest detail would make it possible, to calculate every minor event in the far future, but we know that there are far too many atoms in the universe, where we don't know where they are, and what their movement is. By all practible means it is impossible to predict the future, but that's what random is about: Can we predict it or not. It's not about "Could it be predicted, if ...".

So the statement, that our future isn't predictable doesn't need a proof - it is a fact. A deterministic viewpoint is, what would have needed a proof, but from quantum mechanics we know, that there is uncertainty on the subatomic level (Heisenberg).

  • -1 b/c the "intermixing two things" notion is not really clear (random events are typically defined as one outcome in a set of events with an equal distribution), but also because of the last two paragraphs. We successfully predict the future all the time; it's not even just theoretically possible, it's very practically possible. In a very technical sense, every action we take is a prediction about the state of the world ("I predict when I pick up this cup it will not slip"), but more obvious examples are catching a ball or the weather. Also, uncertainty does not equal randomness. – stoicfury Mar 27 '12 at 3:13
  • @stoicfury: 1st: Many, if not most attributes in nature and society are not equally, but normal distributed. The size of adults in a population for example can have an average at about 1.80m, distributed in a gaussian way. Expected age, income, hair length, number of hairs, weight, speed when running and so on and so on are typically normal distributed. – user unknown Mar 27 '12 at 7:59
  • @stoicfury: 2nd: Of course you think you can predict the future: The bus will arrive in a few minutes, and it arrives in few minutes. With a high probability of 99.99% we get the impression it is for sure. In a practical sense this is a sure outcome. (After the fact, it is, by the way, always a certain event of 100%). But if you should bet a huge amount of money on trivial events, you would feel, that the certainity is limited. (But now I see, I have an error in my second bullet - I'm sorry). – user unknown Mar 27 '12 at 8:09
  • I appreciate the response, although it's not clearly how your 1st response answers anything. I can agree with you there; the fact is that random events aren't supposed to have a predictable (normal) distribution. That is, whether something is random or not, to me is the same thing as whether it has an equal distribution or not. If a set of possible outcomes has a normal distribution, it is not random. If it has an equal distribution, it is random. Maybe I'm missing something here? Re: #2, I don't see how that's an answer either. Your original argument: Things are not predictable. (cont.) – stoicfury Mar 27 '12 at 15:29
  • My counter-argument: Yes, many things are in fact predicatable. Your response: "I can agree with you there"... but sometimes "certainty is limited". Well yes of course; degree of certainty always varies; that's what probability is all about. So I suppose you agree with me, but your original answer still indicates that you think that "So the statement, that our future isn't predictable doesn't need a proof - it is a fact." So... which is it? :P – stoicfury Mar 27 '12 at 15:34

If I collect a series of environmental measurements in replicate, there will be an associated random error component to each of the measurements. Any single measurement will have an equal probability of either being above or below the average; I cannot predict ahead of time which it will be. If the final distribution of measurements is ranked by magnitude, the measurements will be symmetrically arranged around the median value. Any process in control will have random excursions around the mean and will generate a symmetrical distribution; conversely if the excursions are not random and the process is out-of-control, the distribution will not be symmetrical.

  • First off welcome to philosophy.se. The problem here is that you're weaving different meanings of random... – virmaior Jan 28 '15 at 8:01
  • It is not necessary that the chances of the measurement being above and below the average. Take a measurement device which almost always gives 0 and only rarely 10. Then surely the chance of a measurement being below average is higher than the chance of a measurement being above average. – Keelan Jan 28 '15 at 10:20


I 'believe' that if you would copy every single atom there is (universe and whatever there is outside/around) and paste it somewhere (like an other directory on you pc^) the same stuff would happen in both worlds. Every human would do exactly the same and every star and comet would make the same movements.

Ergo: if you would have unlimited mathematical power and knowledge you could calculate what will happen and predict whatever you consider random.

For example: If there was a snapshot of everything (including the movement in every dimension and every other property) of the Mar 20 '12 at 22:31 you could calculate that in 24 hours OP will post this thread.

  • If things are actually deterministic, then the ability to predict the future would hardly be surprising. Any votes for precognition being a reality? – user16869 Apr 29 '16 at 1:57
  • I would agree with your statement if it weren't for the fact that there are "thinking" beings in the original which would become "NOT thinking" beings, in the copy. Even if, somehow, you were able to also copy their information, the original and copy would be the same, only for an instant, then they would diverge. – Guill Oct 24 '16 at 21:57

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