# Logical Error Flashcards

[qwiz] [i]

Logical errors (more precisely known as “formal fallacies”) involve errors that can be reduced to symbolic logic, regardless of the actual content of the argument.  This quiz identifies all the formal fallacies found in 10 Actual Official LSAT Preptests Volume V, using Wikipedia’s name for each error.

PowerScore has trademarked their names for these errors, so the first few entries take PowerScore’s definitions and match them to the Wikipedia names.

[q multiple_choice=”true”] Take a conditional statement (A->B) and then negate both terms (/A=>/B). This logical error is known as:

[f] Well, yes, but that doesn’t help us much here, does it? You can find what PowerScore calls this in Chapter 6 of the Logical Reasoning Bible.

[c] Denying the Consequent

[f] No, that one isn’t a fallacy. If the “consequent” (which the LSAT refers to as the “necessary term” is false, the “antecedent” (a/k/a the “sufficient term”) must also be false.

[c*] Denying the Antecedent

[f] Good! The “antecedent” is the first term in a conditional, which the LSAT routinely refers to as the “sufficient” term.

[q multiple_choice=”true”] Take a conditional statement (A->B), assume the second term is true, and conclude that the first term must be true as well.

[f] Well, yes, but that doesn’t help us much here, does it? You can find what PowerScore calls this in Chapter 6 of the Logical Reasoning Bible.

[c*] Affirming the Consequent

[f] Good! The “consequent” is the second term in a conditional, which the LSAT routinely refers to as the “necessary” term.

[c] Denying the Consequent

[f] No, that one isn’t a fallacy. If the “consequent” (which the LSAT refers to as the “necessary term” is false, the “antecedent” (a/k/a the “sufficient term”) must also be false.

[q multiple_choice=”true”] Only people in group A were cured. Therefore if anyone wasn’t cured, he must not have been in group A.

[c*]  Denying the Antecedent

[f] Correct! You can’t get from C->A to /C->/A. That would be like going from “If I live in California then I live in America” to “If I don’t live in California I don’t live in America.”

[c] Appeal to probability

[f] No, that would mean mistaking a condition that MIGHT happen for  a condition that MUST happen.

[/qwiz]