If we have a certain class of objects and a certain class of relations and if the only questions which we investigate are whether ordered groups of these objects do or do not satisfy the relations, the results of the investigations are called mathematics.
Congress of Arts and Science: Universal Exposition, St. Louis, 1904, (Volume 1), The Fundamental Conceptions and Methods of Mathematics (p. 466), Houghton Mifflin & Co. 1905