Substitution Principle

The Substitution principle is old wine in a labelled bottle. The label is new; the wine has kept many households steady.

Applied daily, it changes less than you hope and more than you expect. That is how principles work — unglamorous, cumulative, and visible only in photographs taken years apart.

The idea is simple, and like most simple ideas it is easy to nod at and hard to use. The nod is free. The use costs attention, every day, in small change.

Watch two shopkeepers in the same lane during a lean month. One cuts quality, the other cuts margin. In a year, one has customers and the other has stock.

Money is a good clerk and a terrible master; the arrangement is entirely up to us. No ceremony needed. Begin with the very next decision.