D.1. The Usefulness of Economic Laws: Scarcity as defined in D.4 of 1.1.1, despite being considered by some as an empirical accident, is a regular phenomenon and thus demands more frequent use of the rules of inference regarding behaviour under scarcity of substitutable means or The Laws of Economics.
E.1. We face scarcity everyday in all matters of choices, in simple or complex dealings, in small scale family or large scale global issues, we always face one single problem that our resources do not permit simultaneous gratification of all ends pursued by us, and this makes scarcity a regularity. We have only 24 hours and no machine can make earth revolve around sun slower than it does, or we have only our own bodies to do our own work and hiring exhausts limited financial resources, or we have only limited information and we know that we do not know all and sometimes cannot know more, or we have resources in a month what our labours can produce for that month regardless of living in a socialist utopia or capitalist reality, our techniques allow to produce only limited quantities. For whatever reason may be invoked, the universality of scarcity is an empirical regularity and it unequivocally implies our means are not fully permissive of simultaneous gratification of all our ends.
If it were not the case, preferences and decisions, thinking and planning, all would not exist. We would gratify at once, and always. And if for nothing else, we all can agree man is but a perpetually wanting animal, and the resources of earth are fixed as is the length of the day.
And so long as our life is marked with choices, so long as we live in a world of relative scarcity of substitutable means, we need reliable rules of inference using which we may navigate our life through the much chaotic, random data generated by the large uncontrolled experiment called life. And these rules of inference are the Laws of Economics.