D.1. Absent Homo-Economicus: During analysis an economist acts as a trustee, and choses the best for the estates they administer without invoking Homo-Economicus.
E.1. from 2.1 it follows that questioning the reasons of choices, or preferences, falls out side the boundaries of economics. Economics takes them as given data. However, given a set of ends, it is reasonable that due to the scarcity of means, anyone would choose the most efficient solution. And so, an economist can safely consider himself to be a trustee of an economic agent facing a set of ends and means. Not only 1.2.1 excludes all hedonism from economics, this additional position of being a trustee, which is logical deduction based on definition of economics, implies that there is no need to assume a Homo-Economicus either.
E.2. A logical derivation of the aforesaid, based on Robbins' An essay on the nature and significance of economic science in order to make the idea more explicit is:
i. The ends are multiple and immutable.
(Ends are given implies they cannot be given up, or added arbitrarily. Treated as the given, they become immutable.)
ii. The means are only partially permissive of gratification of all ends.
iii. The means are also substitutable i.e. exchanged or postponed.
iv. Since the ends are immutable, it is necessary that all ends, or as many as possible, must be achieved by exhausting the given means.
v. If a smaller set of means can gratify an end, the larger number of ends can be gratified.
vi. Therefore, cheaper is preferred to costlier when the cheaper does not thwart our given ends.
vii. If it is possible that more of the preferred ends can be gratified using the given set of means, it is necessary that this possibility is availed (follows from i-vi).
viii. Therefore, maximum of the preferred ends is always chosen given a set of means.
ix. Since, viii follows logically from fundamental problem (1.1.1), it can be treated as a law.
(Formally, the point of tangency between the highest indifference curve and budget constraint.)
x. The premises of this law are immutable ends and scarce means only, and thus exclude any hedonistic calculus or Homo-Economicus.
E.3. This law is only the logical necessity resulting from the fact that ends are immutable, and means are scarce substitutes. So long as an economist treats the subjects of his analysis in such a manner, he treats himself as a trustee for each of them, turn-wise, and in so doing it is acting as a trustee and not invoking any Homo-Economicus that a scientific Analysis of Economics requires. This follows from all preceding propositions.
E.4. Economic Laws are the elucidation of manifold implications of the definition of economics along with added assumptions. In a similar series of deductions (as i to x), one may infer why indifference curves are convex i.e. the lower the quantities of one good compared to its substitute, the higher the relative valuation it receives (Formally, Marginal Rate of Substitution is excessive at larger comparative quantities of one of two substitutes). And from this convex shape, and the aforementioned (tangency condition), one may further derive results such as of a price change, or of income change, or of an imposition of tax, or of a subsidy or of quota etc etc.