In Contrast To Informal Fallacy
As modus ponens, the following argument contains no formal fallacies.
- If P then Q
- P
- Therefore Q
If statements 1 and 2 are true, it will absolutely follow that statement 3 is true. However, it may still be the case that statement 1 or 2 is not true. For example:
- If a scientist makes a statement about science, it is correct.
- Albert Einstein states that all quantum mechanics is deterministic.
- Therefore it's true that quantum mechanics is deterministic.
In this case, statement 1 is false. The particular informal fallacy being committed in this assertion is argument from authority. By contrast, an argument with a formal fallacy could still contain all true premises:
- If Bill Gates owns Fort Knox, then he is rich.
- Bill Gates is rich.
- Therefore, Bill Gates owns Fort Knox.
Though, 1 and 2 are true statements, 3 does not follow because the argument commits the formal fallacy of affirming the consequent.
An argument could contain both an informal fallacy and a formal fallacy yet have a correct conclusion, for example, again affirming the consequent:
- If a scientist makes a statement about science, it is correct.
- It's true that quantum mechanics is deterministic.
- Therefore a scientist has made a statement about it.
Read more about this topic: Formal Fallacy
Famous quotes containing the words contrast, informal and/or fallacy:
“The comparison between Coleridge and Johnson is obvious in so far as each held sway chiefly by the power of his tongue. The difference between their methods is so marked that it is tempting, but also unnecessary, to judge one to be inferior to the other. Johnson was robust, combative, and concrete; Coleridge was the opposite. The contrast was perhaps in his mind when he said of Johnson: his bow-wow manner must have had a good deal to do with the effect produced.”
—Virginia Woolf (18821941)
“We are now a nation of people in daily contact with strangers. Thanks to mass transportation, school administrators and teachers often live many miles from the neighborhood schoolhouse. They are no longer in daily informal contact with parents, ministers, and other institution leaders . . . [and are] no longer a natural extension of parental authority.”
—James P. Comer (20th century)
“It would be a fallacy to deduce that the slow writer necessarily comes up with superior work. There seems to be scant relationship between prolificness and quality.”
—Fannie Hurst (18891968)