The statement that best reveals the author is using the number devil's character to promote a positive view of mathematics is:
"You need one thing and one thing only: one. With one—I am speaking of the numeral, of course—you can do almost anything."
This statement emphasizes the foundational aspect of the number one in mathematics and suggests that with a basic understanding, one can achieve great things in the realm of numbers. It promotes the idea that mathematics is accessible and powerful.