One has to be constantly on guard against treating the material as constant and homogenous. It is as though the fall of the apple to the ground depended on the apple's motives, on whether it was worthwhile falling to the ground,and whether the ground wanted the apple to fall, on the mistaken calculations on the part of the apple as to how far it was from the centre of the earth." John Maynard Keynes' warning against relying on econometric models of his theories.
Academics and aristocrats live in such an uncommon atmosphere that common sense rarely reaches them. Take economists, for instance. Often their basic premise is that economic behaviour is stable and predictable and therefore economic analyses is based on linear relationships. But real-life economics are a complex,
