Handbook of the History of Logic: - Fordham University Faculty

338 Henrik Lagerlund
On Fallacies
The discussion of fallacies is by far the largest part of both Peter’s and William’s
logic books. Their discussion begin by a treatment of disputations. A disputation
is an activity of one person “syllogising” with another to reach a conclusion.
Peter explains, that five things are needed for a disputation, the originator or
the opponent, a respondent, a disputed proposition, the act of disputing and the
instruments of the disputation.
There are four kinds of disputations, namely didactic (doctrinal), dialectical,
probative (temptative) and sophistical. The didactic disputation comes to its
conclusions from premises peculiar to each discipline and not from what seems
true to the respondent. The instruments of such a disputation is demonstrative
syllogisms. A dialectical disputation draws contradictions from probable premises.
Its instruments are the dialectical syllogisms. Probative disputations argue from
what seems true to the respondent. Sophistical disputations argue from what
seems probable but is not. The difference between the last two is that the first
disputation from what seems true or probable to what is true, but the latter from
what seems true or probable but is not.
There are five kinds of sophistical disputations, which derive from the five goals
of such disputations, namely refutation (redargutio), falsity (falsum), paradox (inopinabile),
babbling (nugatio), and solecism (soloecismus). Refutation is the denying
of what was previously granted or granting what was previously denied. Falsity
occurs in the case when a proposition does not conform to reality. A paradoxical
disputation is when the conclusion is contrary to the opinion of the many or the
wise. Babbeling is simply the repetition of the same thing, and finally solecism is
a disputation developing a discourse contrary to grammar.
Peter divides the different fallacies into two major groups and calls the first
group linguistic fallacies and the second group non-linguistic fallacies. The subdivision
is the following:
Linguistic fallacies of:
Equivocation,
Amphibology,
Composition,
Division,
Accent,
Figura dictionis (Figure of speech).
Non-linguistic fallacies of:
Accident,
Secundum quid et simpliciter,
Ignorantia elenchi,
Begging the question,