He also does mention existing notation, and has a discussion on the strengths and weaknesses of various notation forms, e.g.: comparison of dM/dx vs ΔM/Δx vs M′. After reading it, I feel much more comfortable with the soup of new (and re-defined) notation one encounters when reading maths papers. With this presentation, notation becomes just a tool I know how to use, rather than some strange Math fiat delivered from on high.