I generally agree with your comment but have specific disagreements with two parts: Its hard to explain, or even to grasp, how fundamental basic arithmetic is

I generally agree with your comment but have specific disagreements with two parts: Its hard to explain, or even to grasp, how fundamental basic arithmetic is to almost everything in math. I disagree. Not hard to explain at all. Point the person at a page of geometry problems and say, "Imagine struggling with 90 + 90 at the same time as you struggle with the concepts here." Point the person at a page of polynomials to factor and say, "Imagine trying to do these if you hadn't memorized basic multiplication facts." And so on. I still believe that the long division algorithm taught isn't so useful. At the risk of not knowing precisely which algorithm you're talking about, I can't imagine one that doesn't work by taking a large/hard division problem and breaking it down into small/easy division problems. And that's useful because it's a great example of what math does for your thinking. To be specific, I think the important principle math teaches is that, when faced with a big, hard problem, break it down into smaller, easier problems. I would rather describe math as a "learn how to break down problems" discipline rather than use the vague and pretentious "learn how to think" description. All areas of education help your thinking.