One more follow-up regarding the connection between clear thinking and clear writing: Orwell’s famous essay, Politics and the English Language:
A scrupulous writer, in every sentence that he writes, will ask
himself at least four questions, thus: What am I trying to say?
What words will express it? What image or idiom will make it
clearer? Is this image fresh enough to have an effect? And he
will probably ask himself two more: Could I put it more shortly?
Have I said anything that is avoidably ugly? But you are not
obliged to go to all this trouble. You can shirk it by simply
throwing your mind open and letting the ready-made phrases come
crowding in. They will construct your sentences for you — even
think your thoughts for you, to a certain extent — and at need
they will perform the important service of partially concealing
your meaning even from yourself. It is at this point that the
special connection between politics and the debasement of
language becomes clear.
I’ve read this essay numerous times, and it never gets old.