D.1. The Focus of an Economist: The focus and narrowed scope of Economics, the rivet of an Economist, is the set of consequences for our actions, or behaviours, due to the contradiction between given set of scarce-substitutable means, and given set of multiple ends. (from 1.1.1.)
E.1. A study of determinants of means, or determinants of ends, falls outside boundaries of economic science. Hence, any question such as why do we prefer something, why do we have such and such means at our disposal etc etc are all questions of other disciplines, and not of economics. This may be the task of psychology, sociology, biology, history etc. Our narrow task as economists is to study the implications for an individual's behavior of the given set of means which are not fully permissive of simultaneous gratification of all their given ends.
D.2. Given Data: It follows from E.1. that economics treats information about means and ends as Given Data.
Reference: Chapter 02 of Robbins, L. (2007). An essay on the nature and significance of economic science.