D.1. Economically Meaningful: All meaningful in economics is only description of relations based on variations.
E.1. A logical derivation is as follows:
i. Economically Meaningful implies it has Market Interpretation. Since economics began, and remains concerned with study of market.
ii. Market Interpretation implies it can establish, or explain an Economic Relation.
iii. Economic Relation implies agents have their Relative Valuations of means given their ends in mind. (Formally, relative degree of scarcity of means affects rate of substitution of means, given the ends)
iv. Relative Valuation implies Substitution of endowments/means can now take place.
v. Substitution implies: Exchange at the given time, or Exchange over time.
Examples: Exchanging apples with Oranges now (Buying/Selling), or sowing seeds of apples in a garden with expectation of its fruits (Saving/Investment).
vi. Economic Relation also implies non-uniformity of preferences and/or endowments of/between agent(s) who transact. (Already established in preceding observation)
vii. Therefore, Economically Meaningful implies: Relation between non-uniform distribution of means, and ends of different agents based on Relative Valuations of their own means given their own ends.
viii. Or simply, Economically Meaningful implies Relations Among Agents Based on Variations of Their Means and Ends,
ix. Or: Economically Meaningful is Relations Based on Variations.
Remark: This is but only implicit in his writings, and attempt here has been made to make it explicit.
Reference: Chapter 03 of Robbins, L. (2007). An essay on the nature and significance of economic science.