On the Basis for Ethical Conduct
AN 10.1 In a Paticca Samuppada-like sutta the Buddha explains how skillful ethical behavior leads directly to knowing and seeing freedom.
AN 10.2 The Buddha explains why when one has established perfect ethical conduct there is no need to make an effort of will to bring forth freedom from regret, joy, enthusiasm, calm, happiness, serenity, knowing and seeing things as they are, disgust with things as they are, and knowing and seeing freedom, for these things arise naturally as a consequence of perfect ethical conduct.
AN 10.3 The Buddha explains, in a Paṭicca-Samuppada-like sutta, how each step from ethical conduct to freedom from regret, joy, enthusiasm, calm, happiness, serenity, knowing and seeing things as they are, disgust with things as they are, and knowing and seeing freedom depends on the previous condition.
The term to understand here is hat'upanisa. Hata: struck, destroyed. Upanisa (which I take to be from Upanisīdati which lead to Upanissaya (basis, support, foundation)): to set up seated upon. Not 'cause'. So: 'The seating for lack of regret is struck down by lack of ethical conduct. etc.' It is not just that with lack of ethical conduct there is no basis [or 'cause'] for non-regret; lack of ethical conduct actually destroys the basis for non-regret. A person of poor ethical conduct is not just missing out on the benefits of good conduct, he is actively working against his best interests. One is never just passively letting things slide. Poor ethical behavior is a matter of choice. It is not more work to make ethical choices. In fact, since most ethical choices in this system involve abstention from choosing a wrong course, it is much easier to behave ethically. The wording is a matter of the life or urgency of the sutta.