I have a lot of respect for Erik Meijer and I agree with the basic premise of the paper/article. However, I don't fully agree with Erik's position.

Let's say this was my program:

    void Main()
    {
       PureFunction().Run();
       ImpureFunction();
    }

You can always start small and build up something that becomes progressively more stable: no code base is too imperative to benefit from some pure code. Every block of pure code, even if surrounded by impure code, is one block you don't have to worry so much about. Is it fundamentalist programming? Of course not. But slowly building out from there pays you back each time you expand the scope of the pure code.

You won't have solved all of the worlds ills, but you've made part of the world's ills better. Any pure function in an impure code-base is, by-definition: more robust, easier to compose, cacheable, parallelisable, etc. these are real benefits, doesn't matter how small you start.

So, the more fundamentalist position of "once one part of your code is impure, it all is" doesn't say anything useful. And I'm always surprised when Erik pulls that argument out, because he's usually extremely pragmatic.