The Buddha's teaching of karma was a moral exhortation. So it is intended to be seen from the front, to be taken as an answer to the question "how should I behave?" Since people are lazy, and tend to be more interested in saying "How did I get into this mess - surely it was not my fault?", the tendency has always been, probably from the Buddha's day until now, to see the same doctrine from the other other, backwards.
(excerpt from "What the Buddha thought" by R.Gombrich)