strange, shouldn't the be ?I have begun reading Herstein's book, "Noncommutative Rings". I like it very much in general, great style. So if someone reading this hasn't seen it yet, I think I can recommend it.
I'm writing this because I've having difficulty understanding a part of the text about Schur's lemma. I understand the statement and the proof since they're straightforward. What I'm having trouble with is the special case he's talking about later on. He says this:
I understand everything but the last sentence. Are the blocks supposed to be square matrices? Of the same size? What is the quantificator for and