In the preceding chapter, we considered a simplified model of some of the most familiar security problems: authorization, availability, and denial-of-service. If you carefully apply this simplified model to real-world problems, it may make your head spin. Reality is not simplified. To get a grip, in this chapter, we spell out some mathematical details that may help. Every science is characterized by its space. The physical space is a frame of reference between the left and the right, the up and the down, the forward and the backward. The space of security science is the time: it only ticks forward. Its geometry allows expressing availability and authority specifications in simple normal forms.