The word “kamma” has two meanings, depending on context. Primarily, it means intentional actions in thought, word, and deed; secondarily, the results of intentional actions—past or present—which are shaped by the quality of the intention behind those actions.
How do actions determine results? – Skillful intentional acts—those that would lead to no harm for yourself or anyone else—tend toward pleasant results. Unskillful intentional acts—those that would lead to harm for yourself or others, or both—tend toward painful results.
It’s important to emphasize the word tend here, as there’s no ironclad, tit-for-tat deterministic connection between an intentional act and its results. One of the Buddha’s images for kamma is a seed. When you plant a bitter melon seed, it’ll tend to produce a bitter melon vine. When you plant a grape seed, it’ll tend to produce a grape vine. You can’t expect a grape seed to produce a bitter melon vine, or a bitter melon seed to produce a grape vine. That much is certain.
But as to whether either seed will produce a strong, healthy vine depends on more than just the health of the seed. The soil, the sun, the rain all play a role, and then there’s the possibility that the seed might be damaged or destroyed by a fire, eaten by an animal, or squeezed out by plants growing from other, stronger seeds in the field surrounding it.
In the same way, when you plant a “kamma seed,” it’ll tend to give pleasant results if it’s skillful, and painful results if it’s not. For instance, acts of generosity, over the long term, tend to lead to wealth; taking intoxicants tends to lead to mental derangement. But how strong those results will be and how long they will take to ripen will depend on many factors in addition to the original actions: the actions you’ve done before, the actions you’ve done after, and in particular, the state of your mind when the results are fully ripe.
In fact, this last factor—how your mind acts around the ripening of old kamma seeds—is the most important factor determining whether you suffer from those results. If your present actions—your new kamma—are unskillful as they engage with the results of old kamma, you can suffer even from the results of good past kamma. If your present kamma is skillful, it can minimize the suffering that would come from bad past kamma. For instance, if you treat the pleasure coming from past good kamma as an excuse for pride or selfishness, you’re going to suffer. If you treat the pain coming from an unskillful action as an opportunity to comprehend pain so as to release yourself from its power, you’ll suffer much less.
If your intentions influence the quality of the result, does this mean that every action done with good intentions will tend toward a good result? – For an intention to give good results, it has to be free of greed, aversion, and delusion. Now, it’s possible for an intention to be well-meaning but based on delusion, which can easily disguise subtle aversion or greed. When that’s the case, acting on the intention would lead to bad results: believing, for instance, that there are times when the compassionate course of action would be to kill, to tell a lie, or to have illicit sex. To give good results, an action has to be not only good, but also skillful: in other words, free of delusion.
– Karma Q&A, Dhammatalks.org
Acintita Sutta (AN 4:77)
“The Four Imponderables”, “The Four Unknowables”, “The Four Unthinkables”, “The Four Inconceivable”
“There are these four inconceivables that are not to be conjectured about, that would bring madness & vexation to anyone who conjectured about them. Which four?
“The Buddha-range of the Buddhas [i.e., the range of powers a Buddha develops as a result of becoming a Buddha] is an inconceivable that is not to be conjectured about, that would bring madness & vexation to anyone who conjectured about it.
“The jhāna-range of a person in jhāna [i.e, the range of powers that one may obtain while absorbed in jhāna].…
“The [precise working out of the] results of kamma.…
“Conjecture about [the origin, etc., of] the world is an inconceivable that is not to be conjectured about, that would bring madness & vexation to anyone who conjectured about it.
“These are the four inconceivables that are not to be conjectured about, that would bring madness & vexation to anyone who conjectured about them.”