John Q. Mayhem said:Example
Person A: You cannot judge the PHB without reading it.
Person B: Why can I not judge the PHB without reading it?
Person A: Because to judge something you have to be familiar with it. Judgment given in ignorance is worthless.
There is no fallacy or circularity in John Q. Mayhem's argument. Rewritten as a sequence of premises supporting a conclusion (rather than as a conversation) it goes like this:pawsplay said:Also, you've commited a fallacy. "Judgment given in ignorance" assumes "you cannot judge the PHB without reading it" because there may be other ways to judge it. Hence, this still begs the question. If you can state any method other than reading it to "become familiar" then Person A is incorrect. If you can not, then the reasoning is entirely circular.
1. Judgement given in ignorance is worthless.
Therefore,
2. To non-worthlessly judge something you have to be familiar with it.
Therefore,
3. To non-worthlessly judge the PHB you must have read it.
As presented the argument is enthymemic: the suppressed premises are:
1a. One is ignorant of anything with which one is not familiar.
2a. To become familiar with a book you must read it.
2b. The PHB is a book.
Now, premise 1 is unargued but is not simply a restatement of the conclusion 3. Hence, no circularity at that point (ie no begging of the question against someone who denies 3). Furthermore, premise 1 has at least a degree of plausibility.
Premise 1a is also somewhat plausible, and is not simply a restatement of any of the subsequent steps of the argument; hence we can (at least tentatively) deduce 2 without circularity.
Premise 2, combined with 2a and 2b, entails the conclusion 3. Now premise 2b seems pretty certain, so the only controversy is with premise 2a.
As suggested by Pawsplay, premise 2a is contentious. But it is not simply a restatement of the conclusion - it is a claim about how one comes to know a book (and hence does not beg the question against someone who denies 3 - to deny 3 is not to take any stand on how one comes to know books). Hence there is no circularity. It is certainly not the case that, if one can (truly) state no other way of becoming familiar with a book, then the argument is circular. If there really was no other way of becoming familiar with a book than by reading it, then 2b would be true, and the conclusion 3 would follow given premises 1 and 1a.
The natural response of someone who denies 3, but accepts premises 1, 1a and (the incontravertible) 2b is to deny 2a. But to do so is not to diagnose any fallacy - it's just to take part in a garden-variety argument.
My general experience on ENworld is that many posters are far too quick to diagnose fallacies, when in fact what they really have in front of them are perfectly valid arguments (ie the premises really do support the conclusion) which just happen to contain one or more premises that are disputable. In John Q. Mayhem's case, premise 2a may be false, but the argument is not fallacious.
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