Another perspective on economics as a theory of choice is gained by remembering that neoclassical choice theory is a statement of commercial logic, where there is a numeraire and a clear priority. In the 15th and 16th centuries in Western Europe, the innovation of double-entry bookkeeping and spreading use of a standard money as a numeraire made it possible to measure well costs and revenues. In the case of commercial establishments in a commercial system, survival requires that revenues equal or exceed costs over some reasonable period of time. Rationality can be precisely defined. This logic spread to be used by households, family farms, government agencies, etc. and as it has spread this commercial logic has come to be thought of as Rationality. However, there are many forms of rationality, which is to say many bases for purposful action. In some cases there is simply no easily employed numeraire and in many cases there may be multiple goals. Fortunately, not all of life is a simple matter of applying a commercial logic. Anne Mayhew