# William Lane Craig says you can disprove a negative **URL:** \ **Category:** Great Debates\ **Created:** [November 27, 2014, 3:17pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762 "2014-11-27T15:17:43Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [November 28, 2014, 11:44am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/21 "2014-11-28T11:44:39Z")
> [@Giles](#): > > Right – that might be hard in some cases, but easy in others. For example, none of my sisters live in Africa (because I have no sisters), and none of my brothers live in Africa (because I have one brother and he lives in Australia). You’d first have to prove to me that you have no other sisters or brothers. ---
**Author:** ![Reno\_Nevada](https://avatars.discourse-cdn.com/v4/letter/r/6f9a4e/32.png) [@Reno\_Nevada](https://boards.straightdope.com/u/Reno_Nevada)\ **Post date:** [November 28, 2014, 3:42pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/22 "2014-11-28T15:42:26Z")
Negative statements tend to be easy to \*disprove \*and hard to _prove_. \*\*There are no lions in Africa \*\*is easy to disprove, all we have to do is find one; \*\*there are no black swans \*\*is hard to prove. So, the statement \*there is no God \*should be easy to disprove; just demonstrate a God. It is, however, hard to prove. ---
**Author:** ![Lamia](https://avatars.discourse-cdn.com/v4/letter/l/8e7dd6/32.png) [@Lamia](https://boards.straightdope.com/u/Lamia)\ **Post date:** [November 28, 2014, 9:19pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/23 "2014-11-28T21:19:45Z")
> [@Robert163](#): > > William Lane Craig says you can disprove a negative. For example, “the are no Lions in Africa” can be disproven. Atheists, agnostics and rationalists use the term “you can’t disprove a negative” to defend such claims, “you can’t prove Jesus didn’t rise from the dead.” So how is the example about Lions and rising from the dead different? (BTW I am not defending Craig’s statements) Others have already pointed out that it’s _proving_ a negative that’s supposed to be difficult, but there’s another problem with your example here. Atheists, etc., are unlikely to be _defending_ the claim “You can’t prove Jesus didn’t rise from the dead.” An atheist would be far more likely to say that there’s no proof that Jesus _did_ rise from the dead, to which some believers might respond “Oh yeah, well, prove he didn’t!” This believer would thus be challenging the atheist to prove, not disprove, a negative. It would make no sense for the atheist to respond by saying “You can’t disprove a negative.” ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [November 28, 2014, 11:08pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/24 "2014-11-28T23:08:35Z")
> [@njtt](#): > > As an unqualified generalization, the claim that “You can’t disprove a negative,” is simply false. “I don’t exist,” “You don’t exist,” try disproving either of those. I think you will find it is not hard. No you can’t. Well, I THINK so anyway 🙂 ---
**Author:** ![Meatros](https://avatars.discourse-cdn.com/v4/letter/m/b4bc9f/32.png) [@Meatros](https://boards.straightdope.com/u/Meatros)\ **Post date:** [November 28, 2014, 11:13pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/25 "2014-11-28T23:13:58Z")
> [@Robert163](#): > > William Lane Craig says you can disprove a negative. For example, “the are no Lions in Africa” can be disproven. Atheists, agnostics and rationalists use the term “you can’t disprove a negative” to defend such claims, “you can’t prove Jesus didn’t rise from the dead.” So how is the example about Lions and rising from the dead different? (BTW I am not defending Craig’s statements) WLC says a lot of things. He’s also equivocating on the term “prove”. That said, I do think you can hypothetically prove a negative (ex. Showing that something cannot exist because it’s definition is logically impossible). ---
**Author:** ![BlackKnight](https://avatars.discourse-cdn.com/v4/letter/b/eb8c5e/32.png) [@BlackKnight](https://boards.straightdope.com/u/BlackKnight)\ **Post date:** [November 29, 2014, 10:43pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/26 "2014-11-29T22:43:36Z")
There is more than one meaning of “prove”. One meaning has to do with using a formal system like mathematics to prove things with absolute certainty (given certain premises). The other common meaning of “proof” implies a substantial amount of certainty, but not necessarily total certainty. This is the meaning of proof we use in legal matters. Actually, this is the meaning of proof we use in damn near _every_ matter other than math. Anyone who thinks it’s impossible to prove any negative claim in either of these senses of “prove” is simply wrong. I think some people get confused because some _specific_ negative claims are impossible to prove _practically_. **Hentor** linked to an article about Russell’s Teapot, which is a terrific example. However, the fact that there are specific negative claims that cannot practically be proved does not imply that negative claims in general cannot be proved. Another issue is when people equivocate on the multiple meanings of “proof”. There are many negative claims that cannot be proven using only math (or some other formal system, devoid of real-world information). But so what? There are many positive claims that can’t be proven that way either, but people don’t go around claiming that, “you can’t prove a positive”. Finally, consider the following variations on the claim that “there are no lions in Africa”: \* 1. There are no married bachelors anywhere. 2. There are no Kryptonians in the arctic. (No Fortresses of Solitude, either.) 3. There are no sasquatches in the Pacific Northwest. 4. There are no living _non-bird_ dinosaurs in Africa. (Almost gave the nitpickers a foothold there. 😉 ) 5. There are no living thylacines in Tasmania. 6. There are no living ivory-billed woodpeckers in Florida. These are all the same type of claim. They are all “negative” claims. If someone wants to make the assertion that “you can’t prove a negative”, they will have to show that all six of the items on the list are fundamentally unprovable. I contend that not only are they all _theoretically_ provable, but that at least the first 4 are _actually_ provable using the normal, standard meaning of “provable”. (Probably the last two as well, unfortunately!) \*(The items on the list mainly differ in the thingy whose existence is in question. There is some difference in the scope of the area where the thingy is alleged not to exist, but there could easily be a second list where the scope is the primary difference - from “there are no elephants on Earth” down to “there are no elephants in my nasal cavity”. The overall point should be clear in any case: the fact that a claim is a “negative” one has no bearing on whether it is provable. The content of the claim itself, along with the nature of the world and / or formal system in question are what make the difference.) As for Craig, I think the best response to “You can’t prove Jesus _didn’t_ rise from the dead!” is “We don’t have to.” ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [November 30, 2014, 3:27pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/27 "2014-11-30T15:27:32Z")
There’s also a simple logical problem with the assertion that ‘you can’t prove a negative’: since it’s a negative, it would imply that we couldn’t ever know that it’s true, or that if we knew it to be true, it’d be false. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [November 30, 2014, 5:44pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/28 "2014-11-30T17:44:37Z")
Craig’s argument, as summarized in the OP, is a stawman argument. Atheists don’t make the claim that “you can’t disprove a negative”. That is, any atheists with a clue about rhetoric don’t. So, Craig’s argument (if correctly presented above) doesn’t illuminate anything. ---
**Author:** ![Learjeff](https://avatars.discourse-cdn.com/v4/letter/l/94ad74/32.png) [@Learjeff](https://boards.straightdope.com/u/Learjeff)\ **Post date:** [November 30, 2014, 5:45pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/29 "2014-11-30T17:45:37Z")
> [@Half\_Man\_Half\_Wit](#): > > There’s also a simple logical problem with the assertion that ‘you can’t prove a negative’: since it’s a negative, it would imply that we couldn’t ever know that it’s true, or that if we knew it to be true, it’d be false. 🙂 ---
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [November 30, 2014, 9:04pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/30 "2014-11-30T21:04:19Z")
> [@Learjeff](#): > > Craig’s argument, as summarized in the OP, is a stawman argument. Atheists don’t make the claim that “you can’t disprove a negative”. That is, any atheists with a clue about rhetoric don’t. So, Craig’s argument (if correctly presented above) doesn’t illuminate anything. Also you’ll find that most atheists don’t make any claim _at all_. i.e. they say (I certainly, and _very carefully_ say ) something along the lines of " I don’t have a belief in gods or god" and do not say that they _know_ god doesn’t exist, because that is a very definite claim and not one that can be shown to be true to the satisfaction of a theist. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [December 1, 2014, 2:16am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/31 "2014-12-01T02:16:12Z")
> [@Novelty\_Bobble](#): > > Also you’ll find that most atheists don’t make any claim _at all_. i.e. they say (I certainly, and _very carefully_ say ) something along the lines of " I don’t have a belief in gods or god" and do not say that they _know_ god doesn’t exist, because that is a very definite claim and not one that can be shown to be true to the satisfaction of a theist. And in fact what we do say is that it is up to the theist to give strong evidence for the extraordinary claim that Jesus rose from the dead. If we are asked to accept the resurrection without such evidence, theists must accept the possible existence of lots of other gods, and of all sorts of claims about their god. Existential negatives can be hard to prove, depending on the claim - though the claim of no elephants in the house is one which is set up to be simple to prove. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [December 1, 2014, 3:04am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/32 "2014-12-01T03:04:54Z")
> [@Grumman](#): > > The ability to prove [or disprove] a negative depends on how much access you have to the area in which the positive is alleged to have happened. For example, I can prove there isn’t an elephant in my house because I can divide the house into smaller than elephant-sized chunks of space and verify that there is no elephant in any of them. I cannot provide such a strong proof that Jesus did not rise from the dead because all evidence for or against is two thousand years old and on the other side of the planet. Exactly. It can be done in situations where you can exhaustively examine the entire area in question. The dictum, “You can’t disprove a negative” usually implies cases where you can’t exhaustively search the space in question. It would be hard to prove that there is no “bigfoot” in North America, because we can’t search every cubic foot of the continent. ---
**Author:** ![Jragon](https://avatars.discourse-cdn.com/v4/letter/j/e19b73/32.png) [@Jragon](https://boards.straightdope.com/u/Jragon)\ **Post date:** [December 1, 2014, 3:40am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/33 "2014-12-01T03:40:15Z")
In math, generally it’s most difficult to prove “for all” statements, but relatively easy to prove “existence statements”. (This ignores some cases like P=NP where proving an existence statement is equivalent to proving a for all statement, but it holds in a fuzzy sense). So saying “all x are y”, and “no x are y” are both pretty hard to prove, but “at least one x is a y” is fairly straightforward. This is true in real life too, due to the empirical nature of logic in it. I don’t have access to ALL sheep, so it’s difficult for me to say something about all of them. The things I can say are generally matters of definition – all living adult sheep have hearts. The difficulty real life presents compared to math is that our axioms aren’t self-contained, they’re subject to change. The very concept of falsifiability throws a huge wrench in proving any for all statements. In math, we know (or can construct), a-priori, the properties of everything we’re describing. So we can say “assuming all this is true (and we know it’s true), this must be true for all of them.” In real life, we can say “assuming all this is true, this must be true for all of them.” But we don’t generally have access to the data for “assuming” to be right. We know this is true for some extremely large number of data points, but we can’t exactly hack the universe and get the axiomatic definition of energy. All we can say is that we assume with high confidence, which is good enough most of the time. (Of course, do note that what I say also means certain existence statements are difficult to prove. If every existence statement was trivial, then it would be easy to disprove “assuming all this is true” because it would be trivial to prove the existence of a counterexample) ---
**Author:** ![bengangmo](https://avatars.discourse-cdn.com/v4/letter/b/50afbb/32.png) [@bengangmo](https://boards.straightdope.com/u/bengangmo)\ **Post date:** [December 1, 2014, 6:56am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/34 "2014-12-01T06:56:54Z")
Why is it that claims like this are always related to religion? While it’s true that I can’t prove Jesus didn’t rise from the dead, neither can someone prove that he was dead when entombed. Or a slightly different way to put it - try proving that Barack Obama is not a rapist. ---
**Author:** ![EdwinAmi](https://avatars.discourse-cdn.com/v4/letter/e/5fc32e/32.png) [@EdwinAmi](https://boards.straightdope.com/u/EdwinAmi)\ **Post date:** [December 1, 2014, 7:04am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/35 "2014-12-01T07:04:17Z")
theists who are also serious about reason freely admit that God is an invisible dragon (from the Feynman lecture, I think). They just don’t care, because their religion isn’t science. They have faith and believe in their religion for practical, spiritual, and whatever other reasons. ---
**Author:** ![Novelty\_Bobble](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Novelty\_Bobble](https://boards.straightdope.com/u/Novelty_Bobble)\ **Post date:** [December 1, 2014, 8:26am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/36 "2014-12-01T08:26:27Z")
> [@bengangmo](#): > > Why is it that claims like this are always related to religion? Because it is one of the slippery methods that religions commonly rely on. Religions made all sorts of definite claims for their deities in the past. They caused storms, illness, earthquakes, floods etc. Once science offered an alternative theory that worked and had predictive value, these claims were tempered. How many religions now seriously make claims about physical interventions in the natural world? No, the claims now made for gods are carefully worded so that they can’t be disproven (god is love? god sees everything? trliogies?) and to sceptics the tactic is to ask them to _disprove_ these nebulous claims. Of course that is usually impossible to do and my response will always be…you make the claim, you provide the proof. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [December 1, 2014, 9:18pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/37 "2014-12-01T21:18:31Z")
> [@bengangmo](#): > > Why is it that claims like this are always related to religion? . . . No…it’s often about bigfoot or UFOs. (Or the “Hidden Variables” alternative to quantum mechanics.) ---
**Author:** ![The\_Other\_Waldo\_Pepper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_other_waldo_pepper/32/12370_2.png) [@The\_Other\_Waldo\_Pepper](https://boards.straightdope.com/u/The_Other_Waldo_Pepper)\ **Post date:** [December 1, 2014, 11:35pm UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/38 "2014-12-01T23:35:02Z")
“Can you prove you’re _not_ a vegetarian?” “Can I finish eating this burger first?” ---
**Author:** ![Robert163](https://avatars.discourse-cdn.com/v4/letter/r/4af34b/32.png) [@Robert163](https://boards.straightdope.com/u/Robert163)\ **Post date:** [December 2, 2014, 12:21am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/39 "2014-12-02T00:21:47Z")
> [@Lamia](#): > > Others have already pointed out that it’s _proving_ a negative that’s supposed to be difficult, but there’s another problem with your example here. > > Atheists, etc., are unlikely to be _defending_ the claim “You can’t prove Jesus didn’t rise from the dead.” An atheist would be far more likely to say that there’s no proof that Jesus _did_ rise from the dead, to which some believers might respond “Oh yeah, well, prove he didn’t!” This believer would thus be challenging the atheist to prove, not disprove, a negative. It would make no sense for the atheist to respond by saying “You can’t disprove a negative.” thats what i was trying to say maybe i got the terms mixed up ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [December 2, 2014, 1:04am UTC](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762/40 "2014-12-02T01:04:48Z")
> [@Trinopus](#): > > No…it’s often about bigfoot or UFOs. Actually, I’ve read way too much about ufos, and the claims are about evidence supposedly showing they exist. Bigfoot also. I don’t recall any saucer fans claiming that the existence of Bigfoot or aliens buzzing us should be the default belief. The lack of evidence for either - and the debunking of presented evidence - explains why there are more churches than Bigfoot fan clubs. Religion has pretty much gone from claiming that evidence exists to claiming that the existence of evidence would somehow hurt faith or something. [Previous page](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762.md?page=1) [Next page](https://boards.straightdope.com/t/william-lane-craig-says-you-can-disprove-a-negative/705762.md?page=3)