Duty is described as "A note on the chief rules of practical conduct to be observed by those who accept the Law of Thelema." It is not a numbered "Liber" as are all the documents which Crowley intended for A∴A∴, but rather listed as a document intended specifically for Ordo Templi Orientis. There are four sections:
- A. Your Duty to Self: describes the self as the center of the universe, with a call to learn about one's inner nature. Admonishes the reader to develop every faculty in a balanced way, establish one's autonomy, and to devote oneself to the service of one's own True Will.
- B. Your Duty to Others: An admonishment to eliminate the illusion of separateness between oneself and all others, to fight when necessary, to avoid interfering with the Wills of others, to enlighten others when needed, and to worship the divine nature of all other beings.
- C. Your Duty to Mankind: States that the Law of Thelema should be the sole basis of conduct. That the laws of the land should have the aim of securing the greatest liberty for all individuals. Crime is described as being a violation of one's True Will.
- D. Your Duty to All Other Beings and Things: States that the Law of Thelema should be applied to all problems and used to decide every ethical question. It is a violation of the Law of Thelema to use any animal or object for a purpose for which it is unfit, or to ruin things so that they are useless for their purpose. Natural resources can be used by man, but this should not be done wantonly, or the breach of the law will be avenged. For instance, deforestation can cause soil erosion.