It is almost as hard to define mathematics as it is to define economics, and one is tempted to fall back on the famous old definition attributed to Jacob Viner, "Economics is what economists do," and say that mathematics is what mathematicians do. A large part of mathematics deals with the formal relations of quantities or numbers.
Kenneth E. BouldingA somewhat casual observer from outer space might well deduce that the course of evolution in this planet had produced a species of large four-wheeled bugs with detachable brains; peculiar animals which rested when they sent their brains away from them but performed in rather predictable manner when their brains were recalled.
Kenneth E. Boulding[The notion of equilibrium] is a notion which can be employed usefully in varying degrees of looseness. It is an absolutely indispensable part of the toolbag of the economist and one which he can often contribute usefully to other sciences which are occasionally apt to get lost in the trackless exfoliations of purely dynamic systems.
Kenneth E. Boulding