Professor Llewellyn claims that the number of promises made in society has risen over time from early history to the present. He claims that reliance on promises has grown as the number of promises made has grown. He claims that in early history, the rule for enforcing promises was that they shall not be enforced unless a specific good reason is shown. Now, Llewellyn says, promises are enforced unless good reason is shown that they shouldn’t be enforced.
This is not to say that all promises are enforced. But more and more promises are being enforced over time.