Regarding the monastic rules, the Buddha constantly reminds his hearers that it is the spirit that counts. On the other hand, the rules themselves are designed to assure a satisfying life, and provide a perfect springboard for the <answer>higher attainments</answer>. Monastics are instructed by the Buddha to live as "islands unto themselves". In this sense, living life as the vinaya prescribes it is, as one scholar puts it: "more than merely a means to an end: it is very nearly the end in itself."
The rules are a perfect springboard for what?
higher attainments