Karma

The law of karma, says only this:
`for every event that occurs, there will follow another event whose existence was caused by the first, and this second event will be pleasant or unpleasant according as its cause was skillful or unskillful.'

A skillful event is one that is not accompanied by craving, resistance or delusions; an unskillful event is one that is accompanied by any one of those things.
(Events are not skillful in themselves, but are so called only in virtue of the mental events that occur with them.)