The purpose of this complex text is found in the final pages in the consideration of the articulation or relation between two types of power: auctoritas and potestas. The assumption is that a state of exception suspends potestas of publically sanctioned governmental power, by applying auctoritas, sovereign power. What Agamben discovers is that this state of exception is not exceptional but omnipresent, and that rather than there being two types of power, power is nothing other than the fictional and machinelike constant interaction between government requiring a sovereign to legitimate its decisions and sovereignty needing government to makes its power actual in the world.
One can see here that Agamben is using Foucault’s governmentality, but suggests that this did not develop over time, but that sovereign and governing power are fundamentally inter-linked from the start.
The text itself is a crucial articulation between the incomplete portrait of power as sovereignty in Homo Sacer and the final vision of power as the articulation between sovereign power and governance in The Kingdom and the Glory.