The meaning of 'Compulsory.'

Explanation: 'Obligatory' means something required by rule or duty — compulsory. The passage uses it in 'Desirelessness is obligatory,' meaning it is a must.

(1) 'Aphoristic' means expressed in concise principles — unrelated to compulsory.

(2) 'Religious' relates to faith and worship — not compulsory.

(4) 'Permissible' means allowed, which is nearly the opposite of compulsory.