In the region of concrete objects, whose properties are causes, and neither merely fictions nor determinations of space (as in Geometry), we meet with another condition of the validity of any argument depending on a definition:  there must not only be objects corresponding to the definition, but there must be no other causes counteracting those qualities on whose agency our argument relies.  Thus, though we may infer from the quality of co-operation connoted by civilisation, that a civilised country will be a wealthy one, this may not be found true of such a country recently devastated by war or other calamity.  Nor can co-operation always triumph over disadvantageous circumstances.  Scandinavia is so poor in the gifts of nature favourable to industry, that it is not wealthy in spite of civilisation:  still, it is far wealthier than it would be in the hands of a barbarous people.  In short, when arguing from a definition, we can only infer the tendency of any causal characteristics included in it; the unqualified realisation of such a tendency must depend upon the absence of counteracting causes.  As soon as we leave the region of pure conceptions and make any attempt to bring our speculations home to the actual phenomena of nature or of human life, the verification of every inference becomes an unremitting obligation.

CHAPTER XXIV

FALLACIES

Sec. 1.  A Fallacy is any failure to fulfil the conditions of proof.  If we neglect or mistake the conditions of proof unintentionally, whether in our private meditations or in addressing others, it is a Paralogism:  but if we endeavour to pass off upon others evidence or argument which we know or suspect to be unsound, it is a Sophism.

Fallacies, whether paralogisms or sophisms, may be divided into two classes:  (a) the Formal, or those that can be shown to conflict with one or more of the truths of Logic, whether Deductive or Inductive; as if we attempt to prove an universal affirmative in the Third Figure; or to argue that, as the average expectation of life for males at the age of 20 is 19-1/2 years, therefore Alcibiades, being 20 years of age, will die when he is 39-1/2; (b) the Material, or those that cannot be clearly exhibited as transgressions of any logical principle, but are due to superficial inquiry or confused reasoning; as in adopting premises on insufficient authority, or without examining the facts; or in mistaking the point to be proved.

Sec. 2.  Formal Fallacies of Deduction and Induction are, all of them, breaches of the rule ‘not to go beyond the evidence.’  As a detailed account of them would be little else than a repetition of the foregoing chapters, it may suffice to recall some of the places at which it is easiest to go astray.

(1) It is not uncommon to mistake the Contrary for the Contradictory, as—­A is not taller than B, .’. he is shorter.