On the eve of "Patriot's Day" the leader of the free world said on television that ISIL is not Islamic. I do not know what he meant by those words. I'm not singling him out for criticism for so saying, because his two immediate predecessors have also arrogated to themselves the right to pontificate upon what Islam is or is not.
These events have inspired others to opine on the subject and I recommend Ian Tuttle's essay in National Review. In particular, he cites C. S. Lewis and his defense of the orthodox definition of the word "Christian."
Words, as Rush Limbaugh has asserted, have meanings. What El Rushbo does not say is that those meanings are just another partisan football. We leave that to George Orwell who posited the wide-scale demolition of language known as Newspeak whose purpose was to make disagreement with the regime unspeakable.
Or we can go back further to Lewis Carroll who wrote this exchange between Alice and Humpty Dumpty:
Humpty Dumpty smiled contemptuously. 'Of course you don't — till I tell you. I meant "there's a nice knock-down argument for you!"'
'But "glory" doesn't mean "a nice knock-down argument",' Alice objected.
'When I use a word,' Humpty Dumpty said, in rather a scornful tone, 'it means just what I choose it to mean — neither more nor less.'
'The question is,' said Alice, 'whether you can make words mean so many different things.'
'The question is,' said Humpty Dumpty, 'which is to be master — that's all.'
I think Carroll got it wrong, the question is not "which" is to be master, but "whom" shall be master. Modern rhetoric has often reduced itself to empty power games played by sophists. And this shifting of the meanings of words is mere sophistry.
The savages beheading people and flying airplanes into skyscrapers know precisely what they are and what they mean when they say "Islam." To paraphrase C. S. Lewis, we may call them Bad Islamists, but they are Islamists nonetheless. You may not like this. I know I certainly do not like it. But the facts will not become better through fuzzy thinking.