Given the task definition and input, reply with output. This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Passage: Currently, (2004), there are principles of canon law common to the churches within the Anglican Communion; their existence can be factually established; each province or church contributes through its own legal system to the principles of canon law common within the Communion; these principles have a strong persuasive authority and are fundamental to the self-understanding of each of the churches of the Communion; these principles have a living force, and contain in themselves the possibility of further development; and the existence of these principles both demonstrates unity and promotes unity within the Anglican Communion. Question: What kind of force could the canonical principles be said to have within the Communion?
living