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If you see a lion, you will walk away. If you walk away, it won't eat you.

If you see a lion, then it won't eat you.

My answer said: The argument is valid by modus ponens. Why am I wrong?

Dan
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MethodManX
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    Mostly that the lion is faster than you are. – Will Jagy Jul 31 '13 at 00:26
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    You haven't explained why you think you were wrong in the first place. There must be some context that made you think you were wrong; that same context is needed to understand why. – Carl Mummert Jul 31 '13 at 00:55

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Modus ponens tells you that $P\to Q, P\vdash Q$ is a valid argument.

The argument in the question doesn't look like this at all, nor is it a particular case of a possible generalized version of the above.

Your argument is of the form $P\to Q, Q\to R\vdash P\to R$ and it is valid by the hypothetical syllogism (or reasoning by transivity) inference rule.

Git Gud
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  • @ git gud is that the same as disjunctive syllogism? – MethodManX Jul 31 '13 at 03:06
  • @MethodManX No. The disjunctive syllogysm says that $P\lor Q, \neg P\vdash Q$ is a valid argument. – Git Gud Jul 31 '13 at 08:09
  • @ Git Gud: The choices that I have to choose from are: Disjunctive syllogism, modus tollens, fallacy of the inverse, modus ponens, reasoning transtivity, and fallacy of the converse.

    there's no hypotheical syllogism unless there's another word for it?

     – MethodManX Jul 31 '13 at 17:39
  • @MethodManX Hypothetical syllogism is reasoning by transivity. – Git Gud Jul 31 '13 at 19:19