John Stillwell is my favorite Math author. If you want to understand how set theory constructs everything we know, read one of his books. Stillwell’s last book about “Reverse Mathematics” talks about proofs that construct! If you are a beginner, start with “Elements of Mathematics, from Euclid to Godel” Here are all the links to Amazon http://a.co/1HCAb39 http://a.co/3AaG8vc http://a.co/5cjLCrg http://a.co/go3ySXe http://a.co/grxpT27 http://a.co/ezRFzX8