 Chapter VI (De tribus praedicamentis) of the Regulae deals with motion in three categories: place, quantity, and quality. The first part (de motu locali) deals with the speed or slowness of uniformly or difformly accelerated and decelerated motion considered in its kinematical aspect. The second part (de velocitate motus augmentationis) deals with augmentation understood as pure increase in size, and more specifically with the speed of rarefaction as measured by the effect produced, i.e., by space traversed in time. The third part (de velocitate motus alterationis) is concentrated on mathematical description of variation of intensity in space and time. The prime purpose to be achieved in this chapter is to establish definitions of speed in the three categories of motion. All debated cases are posed secundum imaginationem.