Note 828 — Chapter I · : THE HISTORICAL SCHOOL AND THE CONFLICT OF METHODS
R. (Robert) Richards translation
Marshall, Principles, 4th ed., Book I, chap. 6, § 6.
What we say about the mathematical method does not imply any criticism of the Mathematical method in political economy. To establish mathematical relations between economic phenomena, as Walras and his school did, and to deduce economic conclusions from general mathematical theories are two different things.