Flaws in Reasoning

A flaw in reasoning (also called a logical fallacy) is an error in the logic of an argument — a point where the premises do not properly support the conclusion, even though the author presents them as if they do. Identifying flaws is one of the most frequently tested skills on the LNAT. This lesson covers the most common fallacies you need to recognise.

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Why Flaws Matter on the LNAT

LNAT passages are drawn from opinion pieces, editorials, and argumentative writing. These texts frequently contain reasoning errors — sometimes subtle, sometimes glaring. Questions may ask you:

• "Which of the following is a flaw in the author's reasoning?"
• "The argument is vulnerable to which of the following criticisms?"
• "Which of the following most accurately describes a weakness in the argument?"

You need to be able to name and describe these flaws accurately.

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The Major Logical Fallacies

1. Ad Hominem (Attack the Person)

What it is: Attacking the person making the argument rather than the argument itself.