I am reading An Introduction to Formal Logic by Peter Smith. I was checking if the following argument ( Question no-8, Exercise-1 ) is valid or not:
All the slithy toves did gyre and gimble in the wabe. Some mome raths are slithy toves. Hence some mome raths did gyre and gimble in the wabe.
I concluded that it is a valid argument based on its inference pattern. But in the answer sheet, the author has written following:
This has the look of an inference of the shape: All Ss are G. Some Ms are S. So, some Ms are G.
And a genuine inference of that form will of course be valid. However, our Jabberwockian example is not a genuine inference, since the premisses and conclusion are nonsense, and make no contentful claims. And if it isn’t a genuine inference, where we infer a contentful claim from two other contentful claims, it can’t be a valid genuine inference in particular!
Only assuming that the words (slithy toves, gyre, gimble, wabe and mome raths) are meaningless makes this argument deductively invalid.The problem is that English is not hard and fast language, it cannot be that all meaningful words are written in dictionary. So, shouldn't this argument be valid?