This two sections appear in one assignment mainly due to exigencies of fitting Hart’s ideas into our calendar, but both do concern questions about the source of law: first Austin’s use of the idea of a tacit command or order in his account of customary law and then his use of the idea of “habitual obedience” in his account of the sovereign.
• In reading ch. 3 §3, think how Austin’s idea of a tacit order is supposed to work (see the end of his lecture 1) and think why Hart holds that it doesn’t, but take this also as an opportunity to think further about the significance of custom (which is important for Hart’s own positive view). At the end of the chapter (in the next-to-last paragraph, p. 48), you will find a summary of the main points of its sections 2, 1, and 3 (in that order).
• In §1 of ch. 4, Hart presents one of his criticisms of Austin’s use of the idea of habitual obedience. You should think through the problems that Hart takes the right of succession of sovereigns to raise for Austin’s view that habitual obedience is the basis for sovereignty (there is a summary on pp. 59f). But also think about Hart’s discussion of conditions for the existence of rules on pp. 55-57 and about the idea of an “internal aspect” of rules; these ideas will be important in later chapters.
We won’t look at the remaining sections of ch. 4; but, although Hart does not summarize the points made in this chapter as he did in ch. 3, you can find a statement of its general moral in the paragraph at the middle of p. 77.