# Logical Fallacies **URL:** \ **Category:** Great Debates\ **Created:** [March 25, 2000, 6:59am UTC](https://boards.straightdope.com/t/logical-fallacies/17891 "2000-03-25T06:59:00Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 25, 2000, 6:59am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/1 "2000-03-25T06:59:00Z")
I want to explore the concepts of logical fallacies in general and how they relate to arguments here in GD. You can learn more about basic logical fallacies at: [http://www.infidels.org/news/atheism/logic.html](http://www.infidels.org/news/atheism/logic.html) In [url=http://boards.straightdope.com/ubb/Forum7/HTML/001510.html]Gun Control\*\* SuwaveSkin writes: “Expectations about the effectiveness of stricter gun control were measured by six questions…” This is an example of the fallacy of **argument from popularity**. The classic example of this fallacy is the fact if a majority of people believe the earth is flat, that doesn’t make it so. A poll can be an argument from valid authority when you are considering political activity: The approval of a majority of the citizens generally proves a political claim: e.g. the claim that “96% of Americans believe murder is always wrong” **proves** that murder should be made illegal. However it seems that in this instance (although I couldn’t follow the link) Suave is citing a Canadian poll, which proves nothing about the validity of gun control in general, nor the political feelings of the American people in particular. Later, CalifBoomer writes: “So, just who might the _‘authorities’_ be, if all these are _‘irrelevant’_?” in response to my post that the argument to repeal the Second Amendment makes the Constitution and the Supreme Court’s interpretation irrelevant “ **as authorities**.” The basic fallacy of argument from authority consists of the statement that X is true or false because Y says so. For instance, you might argue that “gun control is false because Charlton Heston says its false”. This is not an argument, it’s a fallacy. It doesn’t disprove the assertion, it’s just a statement without meaning in an argument. Sometimes you can cite an authority’s research as an argument. For instance you might say “Steven Hawking proved that black holes radiate (cite publication).” In this case, you’re using Hawkings authority to lend credence to his proof. However you have to remember that black holes don’t radiate **because** Hawking says so, they radiate because of the laws of quantum mechanics. In a legal argument, the text of the law and the documented intentions of the legislators forms a valid authority, because the participants stipulate to the correctness of the law. In an argument over Constitutional Law (e.g. determining if a law is constitutionally valid), the text of Constitution and the Framer’s intent form a valid authority. When you’re arguing to **change** the Constitution, the Constitution no longer becomes the authority. You can’t say, “You can’t repeal the Second Amendment because The Second Amendment is part of the Constitution.” Likewise, when you’re arguing Christian theology, the Bible becomes a legitimate authority. When you’re arguing the benefits of Christianity vs. Atheism, the bible is no longer an authority: You can’t use its text to **prove** the relative validity of Christianity. Joe\_Cool writes: > [@](#): > > You are so right. There are also way too many people abusing the right to speak and practice their religions freely. And too damned many people abusing their right not to testify against themselves. Too many people taking advantage of the right to be secure against unreasonable searches and seizures and the right to a speedy trial in front of an impartial jury. And too God damned many women, blacks and orientals taking advantage of those stupid amendments that let them vote. This argument displays a classic example of the Straw Man fallacy: Suave’s OP calls for a consideration of Gun Control; Joe\_Cool claims he’s arguing for the repeal of _all_ Constitutional rights. Later CalifBoomer writes, “Using your logic, all the amendments, and the Constitiution itself should be repealed.” This is basically the same straw man that Joe\_Cool had used earlier. One shows the Straw Man fallacy when you misinterpret an opponent’s position, refute the misinterpretation, and claim that you have thereby refuted their original position. Formally: A argues that X is true. B claims that A is arguing that Y is true. B proves that Y is obviously false, thus proving that X is false. For instance: A: “I don’t eat broccoli” B: “You don’t eat any vegetables; If you don’t eat vegetables then you won’t get your vitamins; therefore you should eat broccoli.” In this case, B is constructing a “Straw Man”: Person A never claimed not to eat _any_ vegetables, just broccoli. * * * If Cecil Adams did not exist, we would be obliged to create Him. ---
**Author:** ![TomH](https://avatars.discourse-cdn.com/v4/letter/t/90db22/32.png) [@TomH](https://boards.straightdope.com/u/TomH)\ **Post date:** [March 25, 2000, 11:56am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/2 "2000-03-25T11:56:00Z")
Interseting observations, but I’m no sure how they could form the basis of a debate, since no reasonable person would disagree with them. You don’t agree? Well, you’re not a reasonable person, then. (The “no-true-Scotsman” move). I think that the argument from popularity can be valid under certain, limited circumstances. For example, when the subject under consideration is something for which popularity is of central importance. For example, it was used (not by me, but legitimately in my view) in the “I hate soccer” thread in the pit to defend the most popular sport in the world. Since sport = low brow entertainment, populatrity is a valid measure of its status. ---
**Author:** ![Gilligan](https://avatars.discourse-cdn.com/v4/letter/g/e0b2c6/32.png) [@Gilligan](https://boards.straightdope.com/u/Gilligan)\ **Post date:** [March 25, 2000, 3:13pm UTC](https://boards.straightdope.com/t/logical-fallacies/17891/3 "2000-03-25T15:13:00Z")
This is a good topic to explore, SingleDad, and thanks for the link. I believe Libertarian occasionally provides a link to a similar reference site of fallacies. For my own use, I keep a small textbook of these things by the desk so I can look them up when an unfamiliar one is used. (_Analyzing Informal Fallacies_, Engel, 1980) I’m wondering if it would be a good idea to keep such a reference somewhere on the board, similar to the abbreviations guide (to explain what things like IIRC and WAG mean), that I think there is a copy of somewhere around here. ---
**Author:** ![CalifBoomer](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CalifBoomer](https://boards.straightdope.com/u/CalifBoomer)\ **Post date:** [March 25, 2000, 5:37pm UTC](https://boards.straightdope.com/t/logical-fallacies/17891/4 "2000-03-25T17:37:00Z")
Single Dad: Once again, having trapped yourself in the cul-de-sac of circuitous rhetoric, you’ve chosen to abandon the thread in which even you perceive your plight, begin yet another thread from whence you climb to the top of your imaginary _Mt. Logic,_ withdraw into the cave of atheism, and disdainfully proclaim that anyone who doesn’t agree with you is ‘irrational.’ In support of this pedantic activity, you then proceed to post a link to an atheist website, replete with latin phrases (intended, no doubt, to lend an austere legitimacy to an otherwise indefensible position). _My God, man, no wonder you’re strung tighter than a banjo string!_ I submit that the source from whence you obtain your indoctrination is flawed: 1. The groups referenced in your link; Alliance of Secular Humanist Societies American Atheists, Inc. American Humanist Association American Rationalist Association Atheist Alliance Atheist United Council for Secular Humanism Freedom from Religion Foundation among others, are highly suspect as a source of objectivity. Having entered the fray armed with nothing more than anti-theist presuppositions, they make the erroneous assumption that human thought processes are unlimited and infallible. This assumption has yet to be proven, and to an objective mind, this premise is no better than the logic presented by a theist. So let’s play a little game. You contend that the Constitution cannot be used as an argument against its own repeal. You call this this the **fallacious use of argument from authority.** Accordingly, I ask you to **support the assumed premise of the infallibility and unlimited scope of human reasoning as a reliable tool to determine truth.** To be consistent with yourself, you must be able to do this according to your own guidelines and those of the atheist website you cited as sacrosanct. In other words, you cannot refer to your own ‘rational/logical’ processes or back to the atheist website as a source. To do so would constitute a **"fallacious use of argument from authority."** I submit that the mere existence of this conundrum defeats your argument(s) and refutes them as _illogical._ BTW, I’ll be out of town attending an accounting software training class until next Wednesday, and will not have the benefit of reading or responding to your renderings in the interim. :: ---
**Author:** ![Joe\_Cool](https://avatars.discourse-cdn.com/v4/letter/j/ecb155/32.png) [@Joe\_Cool](https://boards.straightdope.com/u/Joe_Cool)\ **Post date:** [March 25, 2000, 10:31pm UTC](https://boards.straightdope.com/t/logical-fallacies/17891/5 "2000-03-25T22:31:00Z")
> [@](#): > > Originally posted by SingleDad: > \*\*…This argument displays a classic example of the Straw Man fallacy: Suave’s OP calls for a consideration of Gun Control; Joe\_Cool claims he’s arguing for the repeal of _all_ Constitutional rights. > > Later CalifBoomer writes, “Using your logic, all the amendments, and the Constitiution itself should be repealed.” > > This is basically the same straw man that Joe\_Cool had used earlier. > > One shows the Straw Man fallacy when you misinterpret an opponent’s position, refute the misinterpretation, and claim that you have thereby refuted their original position.\*\* All I did was apply the stated reasoning equally to all the amendments. After all, there’s nothing legally special about the 2nd, so why should it be treated any differently? If you had posted my comments in context with Suave’s original post, which doesn’t call for “a consideration of gun control” as you stated it, but calls for repeal of the 2nd amendment on the grounds that people take advantage of and exercise the rights protected by it. Talk about a logical fallacy! Repeal protection of the right to keep and bear arms, because people _gasp_ actually keep and bear arms? Maybe we’re expected to live _unarmed_ and take comfort in the idea that we could arm ourselves if we wanted to. Which would lead to the amendment being repealed. Because people exercised the right that it protected. I fail to see how that makes any sort of sense at all. But it does remind me of a song… > [@](#): > > Number 3 > You have the right to free > Speech as long as you’re not > Dumb enough to actually try it. > –The Clash (“Know your rights” from the album Combat Rock) Eat another hit, Timothy Leary, and leave the constitution alone. * * * ## If you say it, mean it. If you mean it, do it. If you do it, live it. If you live it, say it. Joe Cool ---
**Author:** ![Joe\_Cool](https://avatars.discourse-cdn.com/v4/letter/j/ecb155/32.png) [@Joe\_Cool](https://boards.straightdope.com/u/Joe_Cool)\ **Post date:** [March 25, 2000, 10:34pm UTC](https://boards.straightdope.com/t/logical-fallacies/17891/6 "2000-03-25T22:34:00Z")
> [@](#): > > If you had posted my comments in context with Suave’s original post, which doesn’t call for “a consideration of gun control” as you stated it, but calls for repeal of the 2nd amendment on the grounds that people take advantage of and exercise the rights protected by it. Sorry for the fragment. What I meant to say is: If you had posted my comments in context with Suave’s original post, which doesn’t call for “a consideration of gun control” as you stated it, but calls for repeal of the 2nd amendment on the grounds that people take advantage of and exercise the rights protected by it, they don’t sound so outrageous as you make it seem. * * * ## If you say it, mean it. If you mean it, do it. If you do it, live it. If you live it, say it. Joe Cool ---
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 26, 2000, 12:38am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/7 "2000-03-26T00:38:00Z")
Calif: You ask me to “support the assumed premise of the infallibility and unlimited scope of human reasoning as a reliable tool to determine truth.” In the words of Dogbert: Bah! This board is dedicated to the pursuit of rational inquiry. The rules of rational debate are assumed here. If you come in here, you play by _our_ rules. And our rule is that rationality, logic, and critical thinking are the tools of debate. If you want to post on a board where mysticism, irrationality and sheep-like mindless conformism are acceptable forms of argument, go elsewhere. I challenge you to prove that _any_ form of human thought is infallible and has unlimited scope. You can’t, and until you can, I will at least stick with a mode of thought that has been cranking out truths for 2000 years. * * * If Cecil Adams did not exist, we would be obliged to create Him. ---
**Author:** ![Scylla](https://avatars.discourse-cdn.com/v4/letter/s/a5b964/32.png) [@Scylla](https://boards.straightdope.com/u/Scylla)\ **Post date:** [March 26, 2000, 12:48am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/8 "2000-03-26T00:48:00Z")
“support the assumed premise of the infallibility and unlimited scope of human reasoning as a reliable tool to determine truth.” I understand all the words, but what the hell does that mean? ---
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 26, 2000, 12:51am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/9 "2000-03-26T00:51:00Z")
The OP in question is so ungrammatical that it’s hard to really tell what he’s going for. The phrase “way too many people who take advantage of our “right to own guns” or so they think” is indeed a poor argument. I admit your refutation is not the straw man I originally thought it. However, even thought Suave wasn’t, you should be precise in your refutation, and quote the passage you’re refuting; otherwise it looks like the refutation applies to the underlying argument. * * * If Cecil Adams did not exist, we would be obliged to create Him. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [March 26, 2000, 4:24am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/10 "2000-03-26T04:24:00Z")
In light of the statement from CalifBoomer > [@](#): > > BTW, I’ll be out of town attending an accounting software training class until next Wednesday, I vote that we move somwhere else by next Tuesday, and don’t leave a forwarding address. 😃 ---
**Author:** ![Joe\_Cool](https://avatars.discourse-cdn.com/v4/letter/j/ecb155/32.png) [@Joe\_Cool](https://boards.straightdope.com/u/Joe_Cool)\ **Post date:** [March 26, 2000, 5:19am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/11 "2000-03-26T05:19:00Z")
> [@](#): > > Originally posted by SingleDad: > \*\*I admit your refutation is not the straw man I originally thought it. However, even thought Suave wasn’t, you should be precise in your refutation, and quote the passage you’re refuting; otherwise it looks like the refutation applies to the underlying argument. > \*\* I concede your point. by the way, the timothy leary comment wasn’t directed toward you. It was at the freakish reasoning he used in the post we were both responding to. * * * ## If you say it, mean it. If you mean it, do it. If you do it, live it. If you live it, say it. Joe Cool ---
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 26, 2000, 7:19am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/12 "2000-03-26T07:19:00Z")
**kaylasdad99:** I’m with you. Everyone come over to my place. I’ll spring for the first keg! ## **Joe\_Cool:** Hey, even if it were directed towards me, I think TL is a righteous dude. Look at his original protocols when he was first researching LSD. The man was a damn good **scientist**. If Cecil Adams did not exist, we would be obliged to create Him. ---
**Author:** ![JonF](https://avatars.discourse-cdn.com/v4/letter/j/cab0a1/32.png) [@JonF](https://boards.straightdope.com/u/JonF)\ **Post date:** [March 26, 2000, 12:51pm UTC](https://boards.straightdope.com/t/logical-fallacies/17891/13 "2000-03-26T12:51:00Z")
CalifBoomer: > [@](#): > > you then proceed to post a link to an atheist website, replete with latin phrases … > I submit that the source from whence you obtain your indoctrination is flawed: > > 1. The groups referenced in your link … are highly suspect as a source of objectivity … the atheist website you cited as sacrosanct. I presume that SingleDad posted particular link because that’s the one he had handy. You have committed an _argumentum ad hominem_ fallacy; “I don’t approve of or agree with the positions of the sponsiring organizations, therefore all the information on their website is wrong”. FYI, that _particular_ page contains information that is not specific to atheists or humanists and is widely available from many sources, including religous sources (for example, [Faithcenter Ministries](http://faithcenter.hypermart.net/), in [Erroneous Methods of Inference](http://faithcenter.hypermart.net/essays/fallinf.htm) and [Amidst](http://www.amidst.net/), at [The Illogic Primer](http://www.amidst.net/tools/illogic/index.html)). Logic is a tool, and the classifications of fallacies are tools. Like all tools, there are situations inwhich they are useful and situations in which they are not. (IMHO, logic is not applicable to the general issue of religous belief, although it is applicable to discussions of religous belief in which the participants claim to be using logical arguments). The Latin phrases are used because that’s the vocabulary that has developed over the centuries that people have found logic useful. If you don’t like calling a thing for driving nails a “hammer”, then feel free to call it something else; but don’t expect people to understand what you are talking about. Tools are useful _prima facie_; you prove their utility by using them. You appear to be claiming that logic is useless. If my interpretation is correct, that’s analogous to claiming that hammers are useless for driving nails. > [@](#): > > I ask you to support the assumed premise of the infallibility and unlimited scope of human reasoning as a reliable tool to determine truth. To be consistent with yourself, you must be able to do this according to your own guidelines and those of the atheist website you cited as sacrosanct. In other words, you cannot refer to your own ‘rational/logical’ processes or back to the atheist website as a source. To do so would constitute a “fallacious use of argument from authority.” I’m not convinced that SingleDad believes in “infallibility and unlimited scope of human reasoning as a reliable tool to determine truth”; that sounds a lot like a “straw man” to me. But I’ll let SingleDad address that question. You claim that he cannot refer to his own rational/logical processes; why not? There is nothing in logic (or, as far as I know, the Bible or the Koran or the Torah or …) that claims we cannot **think**. And it appears to me SingleDad did not refer to that web site as proof of anything. I think he referred to it to allow establishing a common ground of terms and processes. As I pointed out above, that fact that the website is sponsored by institutions you dislike is irrelevant. * * * jrf ---
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 27, 2000, 3:32am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/14 "2000-03-27T03:32:00Z")
Thank you **JoeF** for your very cogent and dispassionate comments. CalifBoomer is starting to torque me up, and I appreciate your calming influence. You are correct that I don’t believe in the infallibility or unlimited scope of _any_ form of human thought. The paradoxical but real beauty of rational thought is that it can be _proven wrong_. If strong contrary evidence surfaces, you must _abandon_ the proposition. If a rational proposition holds up, if new evidence is in accord and contrary evidence does not appear, then the proposition gains strength. Even when a rational proposition is proven wrong, _especially_ then, you learn something; you can form a new proposition that takes into account the new information. An article of faith can never be proven true by an accumulation of evidence; it is _assumed_ to be true, regardless of evidence. It can _never_ be proven wrong; contrary evidence just causes additional convolution and rationalization of the faith. * * * If Cecil Adams did not exist, we would be obliged to create Him. ---
**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\ **Post date:** [March 27, 2000, 4:58am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/15 "2000-03-27T04:58:00Z")
Logic is a useful tool. I find it quite handy, in fact, from time to time, although more often to examine falsehoods, than to reveal truths. The difference is a subtle one, and it is that very subtlety which leaves so many great questions unanswered. When it comes to finding _The Truth_, the matter becomes even more limited in its amenability to logic. There is much in the experience of man that can be examined, and explained in terms of logical truth, and evidence, and the rules of reason. The great strides of our scientific development rest upon these sturdy foundations. Newton’s **Principia** is a seminal influence on the thinking of western civilization, and its precepts are valuable to this very day. Interestingly enough, Sir Isaac devotes a large percentage of the book itself to encouraging the investigators of his time not to rely on his reports of the phenomena he describes, but to recreate the experiments themselves, and see that the results are uniformly similar. The plea for logical investigation comprises much of the work of scientists today, as well. The stuff of science is not a proper set of the Universal Set. There are matters that are not adequately described, nor reliably predicted by the methods of logic. All logic rests on its assumptions, and however much we might wish it were not so, the more reliable the assumptions are, the less able we are to consider matters without them. The limits of reason are not identical with the limits of the universe. What we cannot perceive might exist. What we perceive might have characteristics we cannot even imagine. That said, it is important to understand that while the tools of logic cannot apply to the matters outside of evidence, and science, neither can the goals of debate be rightly considered with respect to them either. I cannot prove that I love you. Love is not proven, nor is it useful to expect or demand proof of it. It still might be, but it cannot be proven. God is not disproved by an absence of evidence that He exists, but it is a fool’s errand to undertake the proof that He does exist. Use a tool for its intended purpose. Let faith reveal God, and let science reveal quantum mechanics. (I have some suspicion that quantum mechanics involves some level of faith, or perhaps even dark arts, but that is another matter.) Politics is not a matter of reason, either, in my opinion. I have not noticed a great abundance of it in my observations of the political processes in my country. Most of the people I know don’t vote at all, and those who do vote have never been able to make me aware of a fundamentally logical basis for their political choices. “I hate Liberals.” may not be a logical reason for making ones selection of candidates, but the right of enfranchisement is not contingent on logical ability. Voting because of race, sex, or religion is a form of prejudice specifically protected by the Constitution. We can vote any way we please, or not at all. Logic seldom matters in this field of consideration, although it is often alluded to, in much the same way as the “strawman” and other logical fallacies are. ## Tris “Having a thing is not always so pleasing as wanting it. It is not logical that it be so, but it is true.” Spock, from The Amok Time. ---
**Author:** ![Joe\_Cool](https://avatars.discourse-cdn.com/v4/letter/j/ecb155/32.png) [@Joe\_Cool](https://boards.straightdope.com/u/Joe_Cool)\ **Post date:** [March 27, 2000, 5:22am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/16 "2000-03-27T05:22:00Z")
> [@](#): > > Originally posted by SingleDad: > **…You can’t, and until you can, I will at least stick with a mode of thought that has been cranking out truths for 2000 years…** In fairness, don’t forget that it also cranks out falsehoods at a much higher rate. Logic is only a tool (albeit a very valuable one), not the answer. Science only advances by proving that it was wrong all along. (help–what’s the actual quote, and from whom?) * * * ## If you say it, mean it. If you mean it, do it. If you do it, live it. If you live it, say it. Joe Cool ---
**Author:** ![NicePete](https://avatars.discourse-cdn.com/v4/letter/n/ee7513/32.png) [@NicePete](https://boards.straightdope.com/u/NicePete)\ **Post date:** [March 27, 2000, 5:32am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/17 "2000-03-27T05:32:00Z")
CalifBoomer: If you don’t recognize the validity of logic as a tool to reach the “truth”, then why participate in an argument about anything? Why criticize anyone else’s analysis of facts and the conclusions they draw from them? As I see it, an argument consists of two (or more) persons examining a given set of facts, then disputing what conclusions may be drawn from those facts. In order for this to be a useful pursuit, there must be only one set of correct conclusions that may be drawn from a given set of facts. Reason says every single time you add 1 plus 1 you get 2. If you question the validity of reason as a truth seeking tool, are you not saying that 1 plus 1 equals 614 this time, and perhaps 73 the next and maybe a tunafish sandwich the time after that? Not to suggest this is an invalid position to espouse. But if you believe this, what is the point of debating issues? There’s no consistency in the universe – no rules. Did a particular set of facts lead us to a particular conclusion? Hmm, interesting, but so what. Next time we have an identical set of facts we could just as validly reach the opposite result! If you don’t believe in the power of logic, why waste your breath on an argument? * * * Plunging like stones from a slingshot on Mars. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [March 27, 2000, 11:36am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/18 "2000-03-27T11:36:00Z")
**SingleDad** > [@](#): > > You can’t [prove that any form of human thought is infallible and has unlimited scope], and until you can, I will at least stick with a mode of thought that has been cranking out truths for 2000 years. I think I know what you mean, but for the sake of those who might misinterpret you, logic does not _produce_ new truth, but merely _discovers_ truth that was already there. We wouldn’t want people to think that the art of rationalizing is the same as the science of reasoning. **Tris** > [@](#): > > All logic rests on its assumptions, and however much we might wish it were not so, the more reliable the assumptions are, the less able we are to consider matters without them. I once attended an argument at another board, where _days_ passed before I realized that my “opponent” did not accept the axiom that A is A. _!_ Since then, I have found it useful to work out even the most primitive working assumptions before even _beginning_ a debate. In the old Atheist Religion thread series (number II, I think), Spiritus and I began working together on a deduction involving natural selection. Based on my prior experience, I insisted that we establish our axioms up front. He agreed. Almost immediately, he became frustrated by my refusal to accept genetic mutation representing a continuity as axiomatic, and became exceedingly irritated. But I tried to make the point then that finding out about our disagreement over a fundamental matter before the debate got started _was a good thing, not a bad thing_. I hung with it until it appeared obvious to me that the issue had changed from whether genetic mutation was continuous to whether I was capable of thinking logically. **Frankd6** > [@](#): > > Reason says every single time you add 1 plus 1 you get 2. You’re right, but just to be sure everybody’s on the same page, that kind of reasoning requires the Induction Axiom. It was Giuseppe Peano (1858-1932) who proved that 1 + 1 = 2, using the five so-called “Peano Axioms”: (1) Zero is a number; (2) Every natural number or zero, a, has an immediate successor a + 1; (3) Zero is not the successor of a natural number; (4) No two numbers have the same immediate successor; and (5) the Induction Axiom, i.e., “any proterty that belongs to zero, and also to the immediate successor of any natural number to which it belongs, belongs to all natural numbers”. His first statement after these axioms was “1 + 1 = 2”. ---
**Author:** ![Sterra](https://avatars.discourse-cdn.com/v4/letter/s/8c91f0/32.png) [@Sterra](https://boards.straightdope.com/u/Sterra)\ **Post date:** [March 28, 2000, 5:12am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/19 "2000-03-28T05:12:00Z")
logic is not logical ---
**Author:** ![SingleDad](https://avatars.discourse-cdn.com/v4/letter/s/9e8a1a/32.png) [@SingleDad](https://boards.straightdope.com/u/SingleDad)\ **Post date:** [March 28, 2000, 6:33am UTC](https://boards.straightdope.com/t/logical-fallacies/17891/20 "2000-03-28T06:33:00Z")
**Libertarian:** When you say, “logic does not produce new truth, but merely discovers truth that was already there,” you are in a sense correct. I can certainly be said that deductive logic merely exposes truths that are “enfolded” in the axioms. But it seems, especially in mathematics, that the the truths found by these means often have the “flavor” of creation, and not discovery. Be that as it may, one of the most profound uses of the tool of logic is to detect contradition. Such was the case with Cantor’s “naive” set theory. Rigorous examination with logic found that his axioms created the possibility of self-referential sets (such as the set of all sets that do not contain themselves) leading inevitably to contradiction. The difficulty with logic in this circumstance is that the application of logic is not _guaranteed_ to find a contradiction; however logic does guaranteed that if you use it properly to find a contradiction, then your axioms are without a doubt fatally flawed. When you combine logic with empiricism, then you get **science** , a very powerful tool indeed. With science, you first use scientific induction to form a hypothesis, then apply logic to that hypothesis to create a prediction. If that prediction fails, then you know **certainly** that your hypothesis is false. Again science is not oriented towards proving truths, but to eliminating falsehood. It takes intelligence and judgement to correctly apply both science and logic. Most especially, you have to be ruthlessly **self-critical**. You have to actively look for the flaws in your reasoning, your hypotheses, your axioms. People could have gone on forever finding “truths” from naive set theory, but they actively looked for a contradiction, and found it. Science and logic, when properly used, neithe create nor discover: They **destroy**. And what they destroy is **falsehood**. What we have left, on any given day, we call the the “truth”. Always limited, always conditional, always subject to new interpretation. But it is strong because it has withstood the greatest destructive forces of the human mind: science and logic. Faith has none of this power: it can never eliminate a falsehood. Rather, at worst, it wraps itself in that falsehood, preserving it and distorting the mind that holds it. At best, it restricts itself to that which can never be seen, never be tested. I respect the faith of others. If they don’t allow their faith to support a falsehood as revealed by logic and science, I am unable and unwilling to refute their position. However, it is faith’s lack of of power to eliminate the false that prevents me from ever adopting it. I will stick to science: I’m never sure that I’m right, but I’m always confident that I’m not wrong. * * * If Cecil Adams did not exist, we would be obliged to create Him. [Next page](https://boards.straightdope.com/t/logical-fallacies/17891.md?page=2)