Sentence:  It is tempting to speculate about the incentives or <WSD>compulsions</WSD> that might explain why anyone would take to the skies in [the] basket [of a balloon]: perhaps out of a desire to escape the gravity of this world or to get a preview of the next; [...]. 
Meaning of the word marked with <WSD> tags:  An irrational need or irresistible urge to perform some action, often despite negative consequences.