[184] Then, when they have made them familiar and thoroughly conversant with these lessons, they set them at exercises, habituate them to work, and require them to combine in practice the particular things which they have learned, in order that they may grasp them more firmly and bring their theories into closer touch with the occasions for applying them—I say “theories,” for no system of knowledge can possibly cover these occasions, since in all cases they elude our science.[101] Yet those who most apply their minds to them and are able to discern the consequences which for the most part grow out of them, will most often meet these occasions in the right way.