As far as I can see, there are no significant arguments against the principle that all events have a cause, which is to say the principle of sufficient reason. (It's important to note that the seemingly identical idea that all effects have causes is a circular argument based on the mutual definitions of "cause" and "effect".) While the idea seems intuitively obvious and therefore self-evident, we hold many counter-intuitive ideas to be true.

Has anyone proposed a serious argument that events sometimes are not caused?

Clarification: The question title may be misleading because it suggests that the question is an epistemological one, but my actual question is metaphysical (or perhaps even ontological). Whether or not we can always (or even ever) know the sufficient reasons for an event is beside the point (unless it can be shown that we always can know the cause of every event).

I've been asked to define what I mean by an event. That's a bit more than I can take on at the moment, but the Stanford Encyclopedia of Philosophy suggests that we have a "prima facie commitment to entities of this sort." If I had to suggest a definition, I'd say an event is a discrete observation or inference about a period of time. That I was married is an event that was observed by many people. That the sun was formed is an event inferred by the current state of the universe. Of course, that definition has an assumption buried in it that makes the question less interesting: inference implies causation. So we need to find a definition that conforms to our intuition of what an event is, but does not implicitly conform to our intuition that events are caused.

For the purposes of this question, the best definition of an event is that it is something that happens. Do things happen for which there is no cause?

  • 1
    +1 I've always dismissed the idea of asking this question myself because I thought the answer to be blatantly obvious (no). However, it is always better to ask and get "no" for an answer then not ask at all and never know for sure. :) I eagerly await references to literature on this idea (if they exist)... ^_^
    – stoicfury
    Nov 17, 2011 at 7:05
  • Does the 'reason' in the principle of sufficient reason have to be a cause?
    – Geoffrey Thomas
    Apr 6, 2021 at 16:04

10 Answers 10


Actually, there are a number of significant arguments against the principle of sufficient reason; you can find them in Sextus Empiricus, Hume, Wittgenstein and Nāgārjuna to name but a few.

In terms of accessibility, I suppose I'd recommend starting with Hume's view, which you can read about in "David Hume: Causation" (Internet Encyclopedia of Philosophy) or "Kant and Hume on Causality" (Stanford Encyclopedia of Philosophy), followed by Wittgenstein on rule-following, which you can read about in Wittgenstein on Rules and Private Language (Wikipedia article about Saul Kripke's book).

Of course, if you are more familiar with classical literature, you can check out Sextus Empiricus (Outlines of Pyrrhonism, Book III, if I recall correctly); similarly, if you are more familiar with Buddhist philosophy, you can begin with Book I of the Mūlamadhyamakakārikā.


I should clarify that none of these thinkers suggest that there are events that are uncaused; this is one of the positions that Nāgārjuna explicitly rejects in the first verse of the Mūlamadhyamakakārikā. Rather, each calls into question the notion of causality, and attacks either the notion of "sufficiency" or the notion of "reason" with regard to the matter.

  • 4
    Although I haven't read Sextus Empiricus, Nāgārjuna, and (regrettably) Wittgenstein at any length, I know that although Hume found no "necessary connexion" between events, he didn't actually suggest that there are events which are uncaused and he agrees that we are still forced to live by live by our notion of causality: "...We are nonetheless always determined to proceed in accordance with this supposition. There is a natural basis or “principle” for all our arguments from experience, even if there is no ultimate foundation in reasoning (EHU 5.4–5; SBN 42–43)".
    – stoicfury
    Nov 17, 2011 at 16:57
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    @stoicfury: Good point. I was attempting to answer the question in the title, not the final query in the text of the question. I'll edit later tonight to reflect this point. Thanks. Nov 17, 2011 at 17:04
  • So this is really an answer to the question of "can we know the cause of all events?" not "do all events have a cause?" The first is really an epistemological question whereas my question is a metaphysical one. ;-) Nov 17, 2011 at 21:36
  • @JonEricson: It's an attempt to answer "Is there a cogent argument against the principle of sufficient reason?" which has metaphysical and epistemological components. One easy entrance to this is through contemplating the logical fallacy post hoc, ergo propter hoc. Nov 18, 2011 at 7:49
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    The question comes down to what we mean by "causality", which is much more complex than people realize. What is the difference between saying "A happened, and then B happened" and "B happened because A happened"? We might suppose, inferentially, that if B happens every time A happens, then we can say that A causes B; but here we are into issues of Humean regularities and Wittgensteinian rule-following. So let us switch tacks for a moment, and suppose there were an uncaused event-- how would we know? What would be the distinguishing characteristic of said event? Nov 18, 2011 at 20:34

I'm not sure the idea of "reason" is sufficiently specifiable for the question to make sense. I am not familiar with arguments that events are not caused, but there are at least a couple of reasons to be worried.

Since quantum mechanics seems non-deterministic, one could argue that things do indeed happen without reason...or one could broaden the definition of "things" and "reason" so that QM fits nicely within the box.

Also, we don't have direct access to causes; all we have is sense data about what is happening. A cause is thus a generalization of a statistical measurement on sense data; a reason invokes the appropriate conditions and causes. However, in certain cases we have dreadfully little statistical data (e.g. how many universe-creation-events have we witnessed, or does it even make sense to think of this as an event?), so there is dramatically less reason to think that all events are caused in such situations.

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    But surely the entire enterprise of quantum mechanics and science in general is predicated on there being causes to all events? Whether or not we can know the cause is an entirely different question. Statistical causes may still sufficient causes even if we can't know deterministically beforehand what will happen. Nov 18, 2011 at 19:56
  • @JonEricson - That depends what you mean by cause. Something caused something from the set {X1, X2, X3, ...} to happen, but "nothing" may have determined which Xi was selected.
    – Rex Kerr
    Nov 19, 2011 at 6:17
  • That seems an argument against determinism, not the principle in question. What I'm asking about is the view that events may have the null set of causes. ;-) Nov 20, 2011 at 20:02
  • @JonEricson - What is an event? If I say that the-photon-passed-through-the-polarizer is the event, then it was necessary for the photon to hit the polarizer, but not sufficient. If I say that the-atom's-nucleus-ejected-an-alpha-particle, it was necessary to have an atom with a nucleus. Events with a null set of causes can't really affect anything that exists, or you can add in whatever the event affects as part of the event (otherwise you can't detect that it happened). That makes them rather limited in everyday experience.
    – Rex Kerr
    Nov 20, 2011 at 22:19
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    @JonEricson - With that clarification, I reiterate that your question is equivalent to asking about determinism, and determinism seems like a bad model given QM: if you ask why did that go left (as the event) the answer is just, because sometimes it goes left instead of right as an answer. That's pretty causeless, even if you can put numbers on the fraction left and fraction right, and it's predictable.
    – Rex Kerr
    Nov 22, 2011 at 19:37

It's difficult to know how an argument against the principle could begin. As humans, we seem to have a deeply ingrained model of the universe that implies all events have causes. Our instinct seems to be to assume a cause without having any explicit evidence that a cause can even exist. Consider the case of the the beginning of the universe. If any event is likely to be causeless, it is that event. And yet, there exist any number of theories that attempt to explain the Big Bang. Our intuition that everything has a cause seems to literally have no bounds—not even the universe can contain it.

One avenue of attack would be to suggest that our model of causation was itself uncaused and therefore it is not reliable. But that naturally leads us to question how we can make an argument against the idea of causation based on the principle of sufficient causes. (I am reminded of Plantinga's concept of defeaters here.) And more damaging, the argument, if it succeeds, merely shows that we can't trust our intuition, not that our intuition is false. It would be an attack on the epistemological question, not the metaphysical one.

We aren't asking about Determinism, which says that if we know the current state of the universe and the rules that govern it we can (in theory) know every other state of the universe. There are certainly good arguments against that hypothesis. And if we could find an argument against the "principle of sufficient reason", we could debunk determinism easily enough. (If things just happen, we can't very well predict them.)

But showing that determinism is a bad model for reality has no bearing on this question at all. If I find a coin on the ground with heads showing, there are any number of ways it could have gotten there. But since we all accept the principle of sufficient reason, we all agree that something must have caused the coin to be there and we all reject the idea that coins spontaneously appear on the ground. Nor is it a problem that the coin is showing heads rather than tails because there exist approximately equal number of causes that result in that state as opposed to the other. A coin carefully balanced on its edge excludes a number of causes, but we are certain that we will eventually find some set of causes that result in that state even if can never be sure which particular cause actualized it.

Quantum mechanics is a model of parts of the universe that suggests a number of counter-intuitive results, but as far as I can tell people who explore the model still expect to discover some set of causes for everything they observe. A simple test of that assertion is to imagine what will happen if a scientist notices something that the theory does not predict. They will likely redo the experiment, reinterpret their results, adjust the theory, or some combination of the above. What they won't do is say, "Oh well. Things sometimes happen that don't have any reason at all to happen."


There's no evidence that disproves the principle of sufficient reason (and precious little that proves it), so we can continue to behave as if it is true without fear of behaving irrationally.

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    You have not properly characterized quantum mechanics. Because of Bell's Inequality, physicists do not expect to find any reason for a particular choice of observable. They have simply expanded their definition of "reason" to include "picks at random from such-and-so probability distribution".
    – Rex Kerr
    Nov 22, 2011 at 21:34
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    @Rex Kerr: I fail to see how our discovery of quantum mechanics is materially different than our discovery of probability. A probabilistic theory of causation is still a theory of causation. But we seem doomed to be talking right past each other, so I think I'll just let this drop, if you don't mind. Nov 22, 2011 at 21:49
  • You're missing the central point. Probability can be used either because there is a cause for each outcome but we do not know it, so we talk about distributions of outcomes instead; or because there is no cause for which outcome, only that there will be an outcome. But I agree that we are talking past each other, so I will stop.
    – Rex Kerr
    Nov 22, 2011 at 21:56

If a cause is itself an event, every cause must also have a cause.

There cannot, then, be an uncaused cause but instead an infinite regress. If, on the other hand, there is an uncaused cause, the Principle of Sufficient Reason is false.

But perhaps a cause is not an event.

  • I made an edit which you may roll back or continue editing. You may see the versions by clicking on the "edited" link above. I think your point is critical: are (all) causes also events? I suspect they are not, which would allow one to have the principle of sufficient reason and also agents causing events without those causes being themselves events requiring causes. +1 Sep 2, 2018 at 1:29
  • Thank you Frank. If a cause is a living or other entity with volition, that cause results from either the will or an autonomic response. Autonomic responses of the kind that generally could be considered causes result from instinct or conditioning. The will results from the sum of our past experiences, interactions, personal preferences and genetic material or heredity. Whether the will or autonomic responses, they too seem to have causes though not easily discovered. If the cause is not such an entity, it too must have a cause. Sep 3, 2018 at 3:07
  • If there were an apparent first cause, it must have some kind of volition. If so, that must have come from something previous even if outside of our own space-time. If not, it must have been in stasis, so how did the stasis end without another cause? Sep 3, 2018 at 3:08
  • Sorry about the multiple posts, it's not letting me edit. If a first cause refers only to the genesis of our space-time and nothing external to it but that cause, I can see why such a stasis is not indicated. Sep 3, 2018 at 3:19
  • I think you made a good point with the suggestion that a cause may not be an event. That would involve some volition or will for it not to be an event. One might be able to say that the principle of sufficient reason does not apply to such agent-based choices but only to events. This is not to say that an agent-based choice does not have constraints or influences which might be events. Just that the choice itself is not an event nor completely determined. As a side note, I almost missed your comments. Use "@" with my name and this will send me a message. Again, welcome to this SE! Sep 3, 2018 at 4:29

The principle of sufficient reason demands that everything must have a reason. So what is the reason for the principle itself? There isn't one - it's simply stated as a brute fact.

I'm consistently bewildered that such a gaping hole goes unremarked upon. The principle immediately fails when it's turned in upon itself.

That doesn't mean it should be tossed out, but it's clear that with a flaw as enormous and self-negating as this it cannot be anything more than a rule of thumb.


Not only is there, some philosophers and it seems most physicists say the original PSR is invalidated by quantum mechanics. Only a weaker version can be defended. One that says roughly "if there is no sufficient reason, there is a sufficient reason for why there is none".

R. Kane A philosopher

"Not every sub-atomic event has a sufficient, i.e., causal, explanation. But when an event does not have a sufficient explanation, it is assumed that there must be a sufficient explanation for why it does not have a sufficient explanation. This latter explanation lies in the laws of quantum physics themselves which yield the uncertainty principle and thereby account for why some events are uncaused" [1]

Robert Nozick Another philosopher

“…it would be foolhardy indeed to place any significant weight upon the necessity or even truth of SR. This century has presented us with a well-developed physical theory, quantum mechanics, that does not satisfy SR. Moreover, theorems show that any theory that retains certain features of quantum mechanics also will not satisfy SR.” [2]

(He also states the PSR doesn't "self-subsume" to provide its own explanation. The PSR only guarantees a sufficient reason/cause, not what it is. This is a purely philosophical argument, different than the main content of my post. It also does not rule out the PSR, rather the PSR needs another sufficient reason to justify itself.)

John Conway A physicist

video: "...this already suggests and in fact the philosopher Robert Nozick sort of thought it proved that how can I say it, well he thought it proved that Leibniz's principle of sufficient reason was false, you will remember Leibniz's principle of sufficient reason I hope, nothing ever happens says Leibniz without there being a sufficient reason why the thing happens and not something else happens. We'll strengthen this so that it really does disprove Mr. Leibniz's principle of sufficient reason. We'll show eventually that not only doesn't - you see what this shows us, that there doesn't exist a function of direction which tells what the spin is until you make the measurement just not there, and in any way I think of it the particle answers you on the fly"

In standard quantum theory, to explain certain experimental results, one must assume objects did not have definite physical states prior to the experiment. This builds off off a century+ of experiments and works by physicists like John Bell, Kochen, and Specker, and later also Conway (above). Assuming locality/local causality - which is very hard to give up for philosophers and physicists (and everyday folk). So only a weaker version of the PSR survives, as highlighted in the first two quotes.

Some philosophers and physicists may disagree, but what I've written seems to be the currently best defended take on things.

  • "In standard quantum theory, to explain certain experimental results, one must assume objects did not have definite physical states prior to the experiment" By "standard quantum theory" do you mean a particular interpretation of quantum theory like the Copenhagen interpretation, rather than the bare predictive framework? Certainly in the many-worlds interpretation or Bohm's interpretation everything has a definite physical state at all times, though in MWI this state would be the wavefunction rather than a definite position.
    – Hypnosifl
    Apr 17, 2021 at 19:37
  • Ya sorry and thank you for correcting and adding some important details
    – J Kusin
    Apr 17, 2021 at 20:30
  • MWI also is not covered by Bell's argument that QM rules out local realism, since it's an implicit assumption in Bell's proof that each measurement on a member of an entangled particle pair yields only a single definite outcome, while the MWI allows for multiple outcomes. See this paper which gives a simple toy model for how you can have Bell inequality violations in a local realist model involving local splitting of the experimenters.
    – Hypnosifl
    Apr 17, 2021 at 22:47
  • Yes I am aware. I left room with "according to standard quantum theory" and "Some philosophers and physicists may disagree, but what I've written seems to be the currently best defended take on things" for MWI and all other competing theories and interpretations. None of it contradicts my writing nor adds much to the OP's question tbqh
    – J Kusin
    Apr 17, 2021 at 23:23
  • I would say that "standard quantum theory" carries no interpretation, it's just the recipe for setting up a wavefunction for a system, evolving it forward, and calculating probabilities when a measurement is made. Bell's theorem is about ruling out certain interpretations of the theory (local realist ones where measurements have unique values, along with a few other assumptions like the 'no-conspiracy assumption'), and perhaps ruling out certain kinds of extensions of the measurable theory (where additional variables might actually turn out to be measurable rather than 'hidden').
    – Hypnosifl
    Apr 17, 2021 at 23:38

If you accept some radical Platonism such as Teg Mark's contemporary Mathematical universe hypothesis, then it implies that the classic necessary truth PSR (principle of sufficient reason, dependent origination/arising, etc) doesn't hold within our contingent (efficient) physical world. According to MUH:

Tegmark's MUH is: Our external physical reality is a mathematical structure. That is, the physical universe is not merely described by mathematics, but is mathematics (specifically, a mathematical structure). Mathematical existence equals physical existence, and all structures that exist mathematically exist physically as well. Observers, including humans, are "self-aware substructures (SASs)". In any mathematical structure complex enough to contain such substructures, they "will subjectively perceive themselves as existing in a physically 'real' world".

The theory can be considered a form of Pythagoreanism or Platonism in that it proposes the existence of mathematical entities; a form of mathematical monism in that it denies that anything exists except mathematical objects; and a formal expression of ontic structural realism.

Some certain weirdness in modern quantum mechanics which may be formulated and explained by abstractly invented math but seemingly contradicts our everyday experience tends to lead to such an extreme Platonistic view, and in fact Teg Mark is a contemporary physicist. Of course there're numerous arguments against MUH due to its apparent radicalness, but once you hold such position, and since math structure is essentially an axiomatic deductive system, so at least the axioms and its associated definitions don't have any sufficient reason to be accounted for within this world (system), which is certainly not what Leibniz conceived to be possible in his mind when he coined this principle. For him, MUH axioms are just like another form of his "first cause" beyond this contingent world...

  • The PSR is often taken to automatically apply to necessary truths so that the only important philosophical question is whether it applies to contingent truths as well (see Leibniz's argument), and couldn't a MUH advocate say that all truths about are universe are necessary ones, part of the "platonic world" of necessary mathematical truths?
    – Hypnosifl
    Apr 17, 2021 at 22:43
  • @Hypnosifl thx for ur question. PSR and PNC is modal necessary for Leibniz, and thus applied in contingent world by such necessity as manifested in the concept of "causality" people understand contingencies as JTB knowledges. Leibniz mainly applied PSR to contingencies and would ask what's the sufficient reason of such axioms of MUH? Of course for platonist like MUHs, they believe closed axiomatic system necessarily and sufficient derive anything else, including self-awareness, no need for any sufficient reason for MUH's axioms to hold. MUH axioms are just like another form of "first cause".. Apr 17, 2021 at 23:12
  • Modern Platonists usually don't say that some non-contradictory axiom systems are true and others false (Euclidean vs. non-Euclidean geometry for example), what's "necessary" are the various if-then statements that a given set of axioms imply a given proposition is proved true or false. If the truths of both Euclidean and non-Euclidean geometries are equally "necessary" in this sense, wouldn't the same be true of more complex mathematical universes with different laws/initial conditions as axioms? Or would you in some sense deny the truths of Euclidean/non-Euclidean geometry are "necessary"?
    – Hypnosifl
    Apr 17, 2021 at 23:44
  • This is a similar modal realism question asked in MUH's wikipedia page (en.wikipedia.org/wiki/Mathematical_universe_hypothesis), "In response, Tegmark notes that a constructive mathematics formalized measure of free parameter variations of physical dimensions, constants, and laws over all universes has not yet been constructed for the string theory landscape either, so this should not be regarded as a "show-stopper". So consistent systems can be all necessary truths, just needs to wait final QM landscape fixed to decide, Tegmark assigns lower "weights" to the more complex structures... Apr 18, 2021 at 0:27

A bit upset to see nobody speak a word here about Schopenhauer. He wrote his doctoral thesis on the scope and limitation of the PSR. It takes familiarity with Kant, but if you have that then it is worth reading it. It's called On the Fourfold Root of the Principle of Sufficient Reason. I also just wrote a blog post about it here.

  • Welcome to the site! I wonder if you would mind summarizing or copying the parts of your blog post that are relevant to my question? For more about what makes up a great answer, see the help center. Apr 8, 2022 at 16:16
  • @JonEricson Sure. If you are familiar with Kant then you will know he splits up existence into two categories - things within the limits of what minds like ours can experience, and things outside those limits. Schopenhauer, writing mostly against the German Idealists like Hegel, wanted to be clear about this distinction because Hegelians had rejected it. Essentially, Schopenhauer's argument re PSR is that, within the world we experience and do science in, PSR holds just fine; when you go beyond the empirical world, though, we can't be sure the principle is still valid. My blog adds detail. Apr 10, 2022 at 13:14
  • @JonEricson To be clear, this means that when we attempt to ground the empirical world in something outside the empirical world, we are unjustified in doing so. PSR couldn't be said to hold in that sphere of reality/existence. Apr 10, 2022 at 13:16

The cogent argument is from physics: The decay of a given radium atom has no cause, it is a probabilistic event. But quantum mechanics (QM) gives the probability of decay of a given atom from a sample of radium atoms, which all have been prepared the same way.

According to the Copenhagen interpretation of QM there are no hidden parameters which give a sufficient cause - not to name a sufficient reason. Since this conclusion has been stated about a century ago, all efforts to find a better theory with hidden variables have ended unsuccessfully. Nevertheless the search goes on.

History shows that questions like these cannot be decided on the basis of philosophical principles. The range of philosophical a priori claims is limited and has to be determined in each single case.

  • Aristotle in his book Physics and Metaphysics pointed out that some philosphers were asking whether 'chance is a cause'. This option has not been explored thoroughly, mostly because determinism since Newton has been firmly rooted in physics to the extent that Many World theorists prefer a deterministic Many Worlds despite the 'incredulity' of a vastly increased unobservable 'multiverse' that this entails. Plus there is the philosophical confusion that physicisys often suffer from as they are not often cognisant of the relevant philosophical literature as in their arrogance they all too ... Apr 8, 2022 at 23:19
  • ... often dismiss it. For example, Hawking, and Susskind are two prime examples. An example of this confusiom is stating that the evolutionary equation in QM is deterministic in ordinary QM when it is not. Can chance be a cause? It often is in human affairs: lady luck favours some and not others. Apr 8, 2022 at 23:24
  • Furthermore, the Copenhagen position derives from positivism or operationalism. It is Bell who showed that hidden variables weren't possible. Apr 8, 2022 at 23:26
  • @Mozibur Ullah Could you please indicate where in the named works Aristotle speaks about „chance as a cause“? – I agree: Bell’s inequalities (1964) are the strongest refutation to date of hidden-variables theories. But the Copenhagen interpretation (1927) already stated: „There seems thus to be no empirical argument against accepting fundamental indeterminism for the microcosm“. arxiv.org/abs/quant-ph/0609184 (p.408)
    – Jo Wehler
    Apr 9, 2022 at 9:14
  • It's in the early chapters devoted to Aristotles theory of causality. The linked article shows that the Copenhagen interpretation was not the only one discussed at the Solavay Conference. And included discussion of de Broglie's pilot wave theory which is a hidden variable theory. Apr 9, 2022 at 13:57

Has anyone proposed a serious argument that events sometimes are not caused?

David Hume was unimpressed with the principle of sufficient reason. It was not so much that events sometimes are not caused, but that the effects of a given action can never be known in advance. Prediction is impossible.

Hume’s example was a hypothetical game of billiards. (Hume, David. 1902. An enquiry concerning human understanding, 2nd Ed. L.A. Selby-Bigge, ed. http://www.gutenberg.org/ebooks/9662, §25). His scenario assumes an observer who, in advance of an observation, knows almost nothing about the world, even about the effects of gravity.

I disagree with Hume about this. But his thinking stands as an example of a major philosopher who thought the principle of sufficient reason as useless.

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    But prediction is possible and causality is something we take account of every day. So the real problem is to show how this can occur if cause is impossible. Hume took this argument against physical cause from al-Ghazali amd Al-Ghazali posited that Allah was the agency that guaranteed causality whilst Kant supposed it was the human mind. Hume himself didn't offer a resolution. Apr 9, 2022 at 18:15
  • Also, I personally wouldn't call Hume a 'great' philosopher. He was a dyed-in-the-wool racist. Me being brown, I don't take too kindly to philosophers who think my father and mother are worthless pieces of s***. Apr 10, 2022 at 2:09
  • @MoziburUllah. What did Al-Ghazali have to say about the principle of sufficient reason? Apr 10, 2022 at 4:30

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