§1. Introduction
Informal fallacy theoretic labels for putative errors in reasoning are seldom informative, and often fail to distinguish errorless from erroneous reasonings, validities from invalidities. In this post the informal fallacy theoretic label petitio principii, also known as begging the question, is used as a case study demonstrating the label’s failure to identify a corresponding error in reasoning. Formal logical analysis is marshalled as a superior strategy for detecting potential errors of reasoning in the vicinity—errors undetected by the petitio principii label.
Previously, <i> arguments liable to appear valid notwithstanding invalidity, and <ii> arguments liable to be taken-true notwithstanding falsity[1] were identified as fallacies. However, the concept of fallacy also has a more capacious extension which enjoys currency in informal fallacy theoretic and indeed even lay fallacy talk.[2] The semantic riches of the target notion in informal fallacy theoretic and lay fallacy talk, however, admit reduction[3] to the following comprehensive fallacy trait inventory (Definition 1.).
DEFINITION 1: A Fallacy is any error in reasoning which may or may not exhibit one or more of the following traits[4]
(i.i.) Attractiveness
(i.ii.) Ubiquity
(i.iii.) Deleteriousness to argument
(i.iv.) Incorrigibility
Call the list of traits (i.i.- i.iv.) enumerated in definition 1 the AUDI fallacy trait inventory. To say fallacies are (i.i.) attractive is to say they appear to be good arguments, though they aren’t. To say they are (i.ii.) ubiquitous is to say they occur across languages and cultures with high frequency.(i.iii.) Deleteriousness to argument implies that the presence of the error weakens or nullifies the argument. Finally, to say they are (i.iv.) incorrigible is to say that reasoners’ awareness of diagnostic criteria fails to reduce incidence. An argument is a fallacy whenever it contains an error in reasoning, and it has none, or one, or more than one of traits (i.i.- i.iv.).
§2. Case Study: Petitio Principii AKA Begging the Question
DEFINITION 1.2: B begs the question against A, or perpetrates the petitio principii, if for A’s thesis “(λ)” B offers as a refutation “(μ)”, “(μ → ¬(λ))” implying “(¬λ)” and one or more of conditions <i.>, <ii.>, and <iii.> as listed below hold.
<i.> A doesn’t maintain that “(μ)”, and “(μ)” isn’t a consequence of anything A does maintain
<ii.> A doesn’t maintain that “(μ → ¬(λ))”, and it isn’t a consequence of anything A does maintain
<iii.> Either “(μ)” or “(μ → ¬ (λ))”, or both “(μ)” and “(μ → ¬(λ)) are not reasonable presumptions, or defaults.
ARGUMENT 1.2.1: If <i.>, <ii.>, and <iii.> are the case and it is the case that (μ) and (μ → ¬(λ)) then B begs the question against A. But, none of <i.>, <ii.>, and <iii.> are errors in reasoning, so, B begs the question against A but does not commit a fallacy.
PROOF: If it is the case that (μ), and (μ → ¬(λ)), and A doesn’t maintain “(μ)”, and “(μ → ¬(λ))”, and neither are “(μ)” or “(μ → ¬(λ))” consequences of anything A maintains, it follows that (¬λ). Suppose, it is the case that (μ), and (μ → ¬(λ)), and A doesn’t maintain “(μ)”, and “(μ → ¬(λ))”, and neither are “(μ)” or “(μ → ¬(λ))” consequences of anything A maintains, and neither “(μ)” nor “(μ → ¬(λ))” are reasonable presumptions/ defaults. Then, it follows that (¬λ).■
ARGUMENT 1.2.2: If it is not the case that <i.>, <ii.>, and <iii.>, and it is not the case that (μ) and not case that (μ → ¬ (λ)), or equivalently it is the case that (¬μ) and ¬(μ → ¬(λ)) then B does not beg the question against A. But, B commits an error in reasoning.
PROOF: Suppose A maintains “(μ)” and “(μ → ¬(λ))”, and “(μ)” and “(μ → ¬(λ))” are consequences of some theses A maintains, and both “(μ)” and “(μ → ¬(λ))” are reasonable presumptions/defaults. Then, if it is not the case that (μ) and not that (μ → ¬(λ)), or equivalently it is the case that (¬μ) and ¬(μ → ¬(λ)), it follows that (λ).■
§3. Discussion
In argument 1.2.1 conditions <i.>, <ii.>, or <iii.> are met, and so B begs the question against A. Furthermore, according to definition 1, B’s refutation is a putatively fallacious argument because it is attractive to B as a refutation of A’s thesis. B’s refutation makes no errors in reasoning; given that it is the case that (μ), and (μ → ¬(λ)), by modus ponens it follows that (¬λ). Formal logical analysis reveals, contrary to what one would expect from the definition of petitio principii (definition 1.2), B’s reasoning is errorless and, so, simply, not a fallacy (definition 1).
In argument 1.2.2 conditions <i.>, <ii.>, or <iii.> are not met, so B doesn’t beg the question against A (definition 1.2). However, B’s refutation is unambiguously a fallacy since it is the case that (¬μ) and ¬(μ → ¬(λ)). And, so, it follows that ¬(¬λ) or simply (λ). As formal logical analysis reveals, contrary to what one would expect from the definition of petitio principii, B’s reasoning is erroneous (definition 1), and, so, constitutes a fallacy.
§4. Concluding Remarks
It is tempting to argue that since A doesn’t in fact maintain “(μ)”, and “(μ → ¬(λ))” in argument 1.2.1 B commits an error in reasoning simply by taking “(μ)”, and “(μ → ¬(λ))” as premises for refuting “(λ)”. However, this is not an effective argument against the analysis prosecuted here because selecting premises not maintained by A is not an error in B’s reasoning; even if it may be counted an argumentative misstep. Reasoning is not itself argument, it is a rule governed procedure variously employed in argument.
Alternatively, one may object that B is simply misattributing premises A doesn’t in fact maintain to A. Even so, premise misattribution is not an error in reasoning. The reasoning from premises B maintains to the negation of A’s thesis is impeccable, so, one cannot say B commits a fallacy—unless one is willing to stretch unreasonably the definition of fallacy to include premise misattributions, and/or inapt premise selection.[5]
Petitio principii, AKA begging the question, is not a fallacy because inapt premise selection and premise misattribution are not errors in reasoning.
NOTES
[1] Arguments may be valid and yet false owing to the presence of [a] false premise[s], or false conclusion: such arguments are “unsound.” Note, unsound arguments are fallacies on both formal and informal theoretic accounts of fallacies.
[2] The AUDI fallacy trait inventory which captures the notion of fallacy used in informal fallacy theoretic and lay fallacy talk is but a subset of the two-pronged definition of fallacy introduced in the previous post. After all, invalid arguments are liable to appear valid because they are attractive, ubiquitous, and incorrigible; and, they’re bad as their occurrence is deleterious to argument. Furthermore, false and unsound arguments are liable to be taken-true for all the same reasons, singly or in various possible combinations, and their utilisation is just as deleterious to argument. Human reasoners tend in general to judge argument merit by argument attractiveness, and argument goodness by familiarity—a function of frequency with which an argument is encountered. Human reasoners tend to make fallacious arguments despite awareness of what makes them fallacious. Not only are fallacies ubiquitous, unfortunately, they are also incorrigible.
[3] This reduction irritates many a lay and professional champion of the informal fallacy theoretic analyses of fallacies. Regardless, it is a high-fidelity reduction which accurately and exhaustively captures the target notions doing duty in the various available informal fallacy theoretic analyses of fallacies.
[4] Woods, John. “Begging the Question is not a Fallacy.” <http://bit.ly/1ivNdmQ>. In this work Woods maintains that all conditions listed under AUDI, here, must be satisfied for an argument to be fallacious. We relax this condition, accepting that even one satisfied condition can suffice in principle for an argument to count as fallacious; so long as it contains an error in reasoning.
[5] We don’t argue for this claim here, but those who think it objectionable may consult Wood’s argument in the paper cited here.