on what the Buddha taught
Kamma is often translated as action.
Kamma has a (different) meaning outside our domain and this now finds its way in.
Kamma in our context does means action. And there are just these three ways in which we can do things: by body, by speech and by intellect. We can only do something just now right this moment and of course, what we do leads to result; we do something precisely because of an expected result. That the exact 'result' (the ripening of an action) is not found out is one thing, it is one of the four unthinkables, but that there is ripening is to be understood. Action is not a matter of believing.
Do yourself a favour and don’t use kamma but use action instead, so that a misunderstanding is more easily spotted by yourself.
Kamma (nt.) action.