Classification of fallacies
There are five broad categories into which fallacies fall. The most
important division is between the formal fallacies and the infor-
mal ones, although there are important distinctions between the
various types of informal fallacy.
Formal fallacies have some error in the structure of the logic.
Although they often resemble valid forms of argument, the
staircase only takes us from A to B by way of cracked or missing
steps. In brief, the fallacy occurs because the chain of reasoning
itself is defective.
Informal fallacies, on the other hand, often use valid reasoning
on terms which are not of sufficient quality to merit such treat-
ment. They can be linguistic, allowing ambiguities of language
to admit error; or they can be fallacies of relevance which omit
something needed to sustain the argument, permit irrelevant
factors to weigh on the conclusion, or allow unwarranted pre-
sumptions to alter the conclusion reached.
The five categories of fallacy are:
- formal
- informal (linguistic)
- informal (relevance - omission)
- informal (relevance - intrusion)
- informal (relevance - presumption)