It is convenient to posit, or "define" a (unique) point at infinity which is the inverse of 0. That way, a lot of propositions work out without extra special ca

It is convenient to posit, or "define" a (unique) point at infinity which is the inverse of 0. That way, a lot of propositions work out without extra special cases. It was misleading of the author to just say "pretend infinity is a real number".