According to the rules of feduralism why would William never be allowed to be a knight?

According to the rules of feudalism, social status and roles were strictly defined by birthright and land ownership. William, being of lower social standing or lacking noble lineage, would not meet the necessary criteria to become a knight, as knights were typically vassals who served a lord in exchange for land. Additionally, the training and resources required to become a knight were usually accessible only to those from noble families. Therefore, William's position in the feudal hierarchy would preclude him from attaining knighthood.