1. As far as I remember, Leibniz (?) wrote something like that:
"a proof is a sequence of definitions."
What is the exact citation and the reference?
2. Also, I would be very grateful for any information about
historical surveys on the subject "Definitions in mathematics":
many great mathematicians were interested in the subject:
Leibniz, Russell, Peano, ...
Thanks in advance,
Victor Makarov, New York City