It is generally considered beneficial to discover some scientific law or invent an object that is said to further the state of mankind. All inventions and scientific discovery hinges in some way on past knowledge. Since knowledge is so instrumental to any form of advancement, are all facts worth knowing?


I've been asked to revise the question and provide a little more information, so I'd like to discuss the various questions that stem from this one. "Facts" are an incredibly broad topic, so here are the four main questions I think will help us arrive at a meaningful conclusion.

  • If an event that has not yet occurred, can knowledge of that event be considered a fact? That is, is the future deterministic?
  • If knowledge of some scientific principle would allow the bearer to perform evil (genocide, famine, earthquake, etc.), is that knowledge still worth knowing?
  • Is there a difference between the effort required to gain a fact and the effort required to retain a fact?
  • Is it possible to quantify the number of facts a person knows?
  • 1
    Welcome! This is definitely an interesting question, but is there any chance I might be able to persuade you to unpack or develop this question a bit more? It's a little hard to see exactly what you are asking the community for an explanation about -- maybe you could clarify your concern here a bit, and perhaps tell us a bit about your context and motivations here? (What have you found out so far? Is there anything you might be reading that made this question urgent or important for you?)
    – Joseph Weissman
    Nov 9, 2011 at 5:22
  • 1
    Sometimes they're worth forgetting :) Dec 10, 2012 at 14:33

8 Answers 8


"Worth Knowing" is not an objective notion, it is entirely relative

The notion of "worth knowing" is entirely dependent on circumstance. It is not worth knowing to me that there is 600 mbps of traffic going through Server X right now, but to the administrator of that server, that's probably a huge deal. Not worth knowing to me, very much worth knowing to him.

The weight of knowledge acquisition

Are all facts worth knowing? At zero cost, sure (i.e. omniscience), but as Michael points out, as soon as there is even the slightest burden acquiring any facts, there become a huge (essentially infinite) number of facts which are no longer worth knowing.

The weight of knowledge maintenance

The human brain, being a finite physical entity, actually has limits in terms of the amount of raw data it can store. No one has ever reached that limit yet (as far as we know), but theoretically schools are going to pack more and more knowledge into kids brains and newspapers will be packed with more than country or global news but galactic news, and perhaps one day storage may be an issue. Even if you were somehow privy to all the facts in the universe, you would lack the space to store them all. Some facts would simply take a lifetime to acquire or not even be possible in practice (P = NP).

Your additional questions not already addressed above:

  • Is it possible to quantify the number of facts a person knows?
    Theoretically, yes, as the brain is a physical organism it is not outside the scope of observation. In practice, we do not have this technology and we probably won't have it for at least another 100 years. You could do it the old fashion way and get a rough count that would provide a relatively consistent measure across the board though; simply have people take every single subject test in the world and count up the questions they got correct. It would be very rough, but have internal consistency. (No, it would not get at little facts like "my sisters blanket has 2 juice stains on it", etc, but general stuff, yes).
  • If an event that has not yet occurred, can knowledge of that event be considered a fact? That is, is the future deterministic?
    If the world is deterministic, then yes, it would be a fact. This is, of course, highly debated however (whether the universe is deterministic or not).
  • I will just point out that when we use world ALL in discussion, it becomes pointless. In this case - exact number of hair (fine threadlike strands growing from the skin) on my head in this second is also a fact. And its absolutely not worth knowing.
    – c69
    Nov 9, 2011 at 19:02
  • @c69: Yes, "all" does make the question different than "some", but I wouldn't say it makes it entirely pointless. As I mentioned, theoretically any fact could be worth knowing to someone in the right circumstance. Perhaps someone out there is trying to enter the Guinness Book for the record of "Person with most hair follicles on their head". Then such a fact would be very much worth knowing to them. ^_^
    – stoicfury
    Nov 9, 2011 at 19:26
  • I recommend looking into the notions of fact-value dichotomy and dangerous knowledge. We also have to be careful when we say that this value is relative because relative means relative to something, and that something requires a metaphysical and anthropological study. I disagree that this relativism is so radical that any fact can be equally as valuable as any other, however that is understood.
    – danielm
    Dec 16, 2012 at 14:28
  • "If the world is deterministic, then yes, it would be a fact." - What do you think of this -> philosophy.stackexchange.com/questions/32463/…
    – IsThatTrue
    Mar 5, 2016 at 19:29

All facts are not worth knowing for the simple reason that most of them don't make any significant difference. For example, knowing the precise position of every iron atom in the earth's core is extraordinarily useless because (1) they won't be there for long, and (2) it doesn't matter anyway, since nothing really interacts with the earth's core in a way that depends in detail on the position of said atoms.

  • But what would happen if you made a novel scientific discovery utilizing that knowledge? How can you know if a fact is worth knowing or not without first knowing it? Nov 16, 2011 at 3:30
  • @ZachRattner - You can predict to a high degree of certainty whether or not the information you would gain will be worth anything. For example, I am pretty sure that analyzing the time between posts I've made will not yield a cure for cancer.
    – Rex Kerr
    Nov 17, 2011 at 4:25
  • It wouldn't help you cure cancer, per se, but what if I was trying to profile you? Knowing the times you go on your computer to participate in discussions like these might be useful then. Nov 17, 2011 at 15:38

Let's try to unpack the question a little bit.

If we begin with: "Are all facts worth knowing?", the immediate answer would seem to be "Sure, why not?" If, for example, some deity were to offer us complete and total omniscience, is there a good reason to refuse?

Lessing famously said he would, under certain conditions:

"If God were to hold in his right hand all the truth and in his left the unique ever-active spur for truth, although with the corollary to err forever, asking me to choose, I would humbly take his left and say 'Father, give; for the pure truth is for you alone!"

This leads us to the fact that knowledge is not generally given directly by a deity, but rather, is earned through varying amounts of effort.

So, now we can restate the question as: "Are all facts worth the effort to uncover?"

I'd argue that the answer here would be "no." It is possible, albeit mind-bogglingly difficult, to count the exact number of grains of sand on the beaches of Hawaii; however, it would appear the the instrumental value of knowing that exact number approaches zero.

  • This is a good start, Michael. But can you really restate the question into terms that focuses on the burden of acquiring all this knowledge? What about the effort required to maintain this knowledge, should you acquire it all at once? In that case, would it still be worth knowing? Nov 9, 2011 at 15:41
  • @ZachRattner: Once there is effort involved (whether in acquiring or maintaining), one can take an instrumentalist approach and weigh the effort versus the expected value. Nov 9, 2011 at 16:33

Let's say I'm reading Murder on the Orient Express and you offer to tell me who killed Mr Ratchett. Arguably, given my current state (half way through M. Poirot's adventure) this is not a fact that it's worth my knowing: it would spoil my enjoyment of the book. [Let's leave aside the factivity of fictional claims. Pretend I'm reading something based on a true story, so there really is a fact of the matter at stake.] So this looks like it's a fact that it's not (right now) worth my learning. Obviously the point of reading through the whole book is to discover exactly this fact so it can't simply be that this is a fact not worth learning. It's just that learning the fact before the proper time reduces my enjoyment of the reading experience.

Let's take another example. Let's say that there is some scientific discovery that, if discovered, would give the discoverer unimaginable power: let's say the discovery is some kind of programmable virus that kills all and only the people it is designed to, or some such. Let's say that this discovery would have no benefits whatsoever, all it would do is give its discoverer the power to bend the world to her whim. Is this a fact worth knowing? Would the world be better off if this fact was simply never learned? Arguably: yes. There's a separate question as to whether there are any such facts with only bad consequences. If there aren't, then maybe scientific knowledge is worth knowing, always.

If you are a Bayesian, then there's a nice theorem due to I.J. Good that if you have a choice between learning something and not learning it, the expectation of the option to learn cannot be lower than the expectation of not learning.


To answer your last sub-question... it's very hard to imagine that there's a good way to quantify the number of facts someone knows because of cases like this:

I know that

(a) my brother was born in 1978. (b) This site, philosophy.stackexchange.com, opened in 2011.

Do I also know

(c) My brother was born before this site was created.

and did I know (c) before starting this answer, given that I had never mentally juxtaposed (a) and (b) before?

It's true that (c) feels kind of "second-order", like the sort of fact you only get from knowing other things. But that's complicated too, because I know

(d) Stack Overflow was created before this site.

I don't know when Stack Overflow started, so (d) isn't (obviously) derivable from other facts that I know. I just know it came first.

And if you declare that to find the size of someone's "real" set of known facts you have to cross out everything they know that's derivable from other things they know... well, that has a whole raft of problems: there's no guarantee of a single answer (one set of propositions can be generated by multiple different minimal sets of axioms), and not everybody knows which of the things they know are derivable from other things they know.

  • This is a good thought, which raises the question of whether it would be useful to introduce a concept of a "class of facts". For example, taking your fact (a), you could also claim that the knowledge of fact (a) is a fact in its own regard ("I know that I know that my brother is born in 1978."). If this is allowed, then anyone who knows one fact knows infinitely many facts. Is there a way you could classify facts according to their prerequisite knowledge, and then only count knowledge of each prerequisite as a proper fact? Nov 14, 2011 at 19:57

Lets assume facts can be numbered off - 0,1,2,3,... So every fact is designated a natural number.

Suppose for a contradiction that there is a fact not worth knowing.

Then there is a fact that is not worth knowing whose designation is least among the designations of facts that are not worth knowing. Call this least designation n.

Now if we knew the fact whose designation is n, then we could deduce n, and thus whenever we encountered a fact with designation strictly less than n, we could immediately deduce that this fact is worth knowing, and therefore proceed to memorize it.

Thus it would be worth knowing the fact whose designation is n. But we assumed that it was not worth knowing! Contradiction.

Therefore, every fact is worth knowing.

Note: this is basically just the interesting number paradox.


You are missing an important dimension here. TIME. Not all facts are worth knowing at any given time, not even at the same time, but right time. You can't handle it. Say for example, a process or system must evolve like X->Y->Z. To get to Y all you need is X, not Z, when you go to Z, you remember or know Y, at that time X becomes ingrained in your mind. Later when you move to Z->A->B->C, you don't even need to remember X. "Last generations knowledge becomes current generation's common sense".

Answering your Questions

If an event that has not yet occurred, can knowledge of that event be considered a fact? That is, is the future deterministic? No, Fact has an hit ratio of 100% (it may vary with the way people perceive, that is another topic). No matter how big is your sample size, all you need is one FALSE to bring your hit percentage to something less than 100.

If knowledge of some scientific principle would allow the bearer to perform evil (genocide, famine, earthquake, etc.), is that knowledge still worth knowing? You need to learn from the past, these events you mentioned has happened before and the root cause is knowing some fact or the other.

Is there a difference between the effort required to gain a fact and the effort required to retain a fact? Yes, the effort required to gain a fact is > effort required to retain a fact. In other words, you don't need anything to retain a fact, you need to give at-least something to gain a fact. People who believe in luck would say "sometimes that later will be zero". But all have to agree, you don't need to do anything to retain a fact, you just let it there float like a ball filled with air on top of water. If it sinks, then it is not a fact. Same way, if you make effort to retain it, it is not a fact.

Is it possible to quantify the number of facts a person knows? Yes. You can count the number of stars on the sky, but when you see a star, you wont know whether it is already counted or not. I would rather blame the geometry of the sky than my counting ability and patience to do so.


I would say NO. Because knowing the event, which will happen in future, earlier than its right time will fall us in disturbed mind state. Let say "If I know, in advance, that I'm going to die next month then I cannot enjoy my present. Whether I have happiness right now or any I am upset right now."

It's not necessary to any person to know all things. Knowing the future events in advance can spoil our present TIME.

If a person know that what he has in his fate, then he will not make any effort to gain it by assuming that it's already in my fate so why to effort?

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