30 THE SCIENCE OF LOGIC 



($) Non causa pro causa, false cause, Trapa TO p&amp;gt;rj atriov to? ainov 

 supposing a conclusion to follow from a premiss which is really 

 irrelevant. 



(6) Consequents, consequent, irapa TO eTropevov assuming that 

 a hypothetical proposition is always and necessarily reciprocal. 



(7) Plures interrogationes, many questions, Trapa TO ra ovo 

 pa)T-qp,aTa ev Troieiv asking a question in such a form that a 

 single answer involves more than one admission. 



(d) Aristotle s distinction between fallacies in dictione and 

 fallacies extra dictionem is not the same as Whately s division into 

 logical, and non-logical or material. By &quot; logical &quot; fallacies 

 Whately meant those in which &quot;the conclusion does not follow&quot; 

 from the premisses ; by &quot; material,&quot; those in which the &quot; conclusion 

 does follow &quot; from the premisses. In the former class, the defect 

 of proof lies either in a manifest violation of some of the formal 

 laws of the syllogism quaternio terminorum, undistributed middle, 

 illicit major, illicit minor, negative premisses, etc., defects which 

 remain even when symbols are substituted for the terms and 

 concepts, and which Aristotle would not regard as sophisms owing 

 to the transparency of the mistake ; or the defect lies in a simi 

 lar violation masked in ambiguous language. The transparent 

 defects Whately called purely logical, the cloaked defects semi- 

 logical fallacies. The latter he regarded as all alike reducible to 

 ambiguous middle term, including in this class all Aristotle s 

 sophisms except the ignoratio elenchi, the petitio principii, and the 

 non causa pro causa. These three he included in his &quot; material &quot; 

 fallacies, by which he understood mistakes due to assuming false 

 or unproven premisses, or premisses which prove the wrong con 

 clusion. Whately s main distinction between formally incon 

 clusive arguments, and other sources of error is sound and in 

 telligible. But his nomenclature is objectionable. It is due to 

 his narrow, nominalistic view of the scope of logic. All fallacies 

 are logical, inasmuch as they are violations of logical principles or 

 canons. Then, although most of Aristotle s sophismata, included 

 in Whately s class of &quot; semi-logical &quot; fallacies, do in fact usually 

 lead to formally invalid syllogisms through ambiguous middle 

 terms, yet this is not clear in regard to some ; and they certainly 

 may lead to error otherwise as well. Hence the attempt to 

 group them under such a head is unsatisfactory. Finally, on his 

 own view of the scope of logic, Whately should not have dealt 

 at all with what he called &quot; non-logical &quot; or &quot; material &quot; fallacies. 



