Final answer:
Without additional context, it's unclear why William purposely loses jousting events. Historical references from Seneca and Tacitus raise possibilities of strategic or philosophical motives but do not directly explain William's actions.
Step-by-step explanation:
The question regarding why William purposely loses jousting events seems to hint at a strategic choice or a moral dilemma he faces. Drawing on the example from sentence 14, 'the skillful fighter puts himself into a position which makes defeat impossible, and does not miss the moment for defeating the enemy,' one might infer that William's actions are strategic in nature - allowing him to control the circumstances of combat for a greater advantage in the long run.
However, there isn't enough context within the provided information to determine a clear reason for William's choice to lose. References to historical texts by Seneca the Younger and Tacitus discuss the nature of games and combat in ancient times, suggesting the possibility of moral or philosophical reasoning behind actions in competitive events, but do not explicitly provide a reason for William's intentional losses in jousting.