This is a line that resonates with me, and the one which some negative comments might overlook (3 hours in, at least):

  "What can you say in this language that would 
  be impossibly inconvenient to say in others? 
  In the process of learning how to say things 
  you couldn't previously say, you'll probably 
  be learning how to think things you couldn't 
  previously think."

This is one of the value propositions of language. It's one of the ways we learn new things, and thus become more capable of doing valuable work as people.

Criticisms of this essay in comments so far have seemed to fall into these buckets:

  1. Lisp? Macros? Boo. (Not novel/too weird/etc)

  2. Languages are solved, not important; I build systems.

  3. I don't like the tone of this essay.

(1) and (3) are side points, unrelated to thesis. (2) is the interesting one, and at the heart of what the essay talks about.

I've always been in the pg camp on this one. Sure, systems are the thing, we can't be purists, etc -- but saying that languages don't matter, for us, would be like rocket engineers saying that materials don't matter.

If you're building a table, you can make it out of almost anything; a table is a solved problem. Wood, carbon fiber, steel.

But at the limits of what's possible, like a rocket, the material's properties, limitations, and weaknesses in extreme circumstances matter.

You can definitely imagine that important things are happening, in the maker's mind, when they start working with a new material, seeing what others are able to do with it, seeing how the making process is easier, or what steps are unimportant/unnecessary now vs. in their usual materials. And that informs their thinking, going forward, about what's possible in systems they might build.