Kamma is the part of Buddhism I arrived already believing. That what you do has consequences that belong to you, and that nobody is going to settle your account on your behalf, is the thing I held before I had a word for it — and finding a tradition with it at the centre is most of why I'm still reading.
Which is exactly why it's worth being careful about. The version of kamma that floats around in general conversation — including among people who consider themselves Buddhist — contains at least three claims the Theravāda texts explicitly reject. Not "nuance", not "a subtler reading". Rejected, by name, as wrong view.
It is defined as intention
The definition is unusually blunt for a term this loaded:
It is intention, monks, that I call kamma. Having intended, one acts by body, by speech, by mind.
Cetanā — intention, volition, the leaning of the mind — is the kamma. The bodily act, the speech, the thought are what follow from it. This is not a technicality; it decides everything downstream. It means the same outward action performed with different intentions is not the same kamma at all, and it means the thing being trained is not your behaviour in the first instance but what your behaviour is coming out of.
It also means kamma is not the result. English collapses the two — "that's his karma" usually points at something that happened to someone. The texts keep them apart: kamma is the intentional action, vipāka is its ripening. Most of the confusion below comes from mashing those two words into one.
What it does not say, three times over
1. That everything you experience was caused by past action
This is the big one, and it is not a matter of interpretation. The Buddha lists three positions held by other teachers and rejects all three: that everything a person experiences is caused by past action, or by a creator god's design, or by no cause at all.
His objection is the same in each case, and it's practical rather than metaphysical: if any of them were true, there would be no ground for saying "this should be done, this should not be done." Nothing you decide now would matter. The moral life would have no purchase. A doctrine that makes intention irrelevant cannot be the doctrine of a teaching whose central term is intention.
So "everything that happens to me is my karma" is not a devout position. It is, specifically, one of the three views the tradition sets itself against — and it has the same defect as fatalism dressed in any other clothes.
2. That your circumstances are a readout of your moral worth
There is a discourse where someone asks the Buddha directly whether everything a person feels is caused by what they did before. The answer is a list of causes, and kamma is one item on it — alongside disorders of bile, of phlegm, of wind, their combination, changes in the weather, careless behaviour, and simple external assault.
Then the sharp part: those who assert that whatever a person feels is caused by past action have gone beyond what they actually know and beyond what is agreed in the world. He calls that wrong.
You can feel how much that cuts against the popular use. Someone falls ill, loses work, gets hurt — and the reflex is to read it as an invoice arriving. The texts say plainly that most of what happens has ordinary proximate causes, and that treating misfortune as a verdict is a claim nobody is in a position to make. Applied to another person it is worse than a mistake: it is a way of making their suffering their fault while sounding spiritual about it.
3. That the same deed carries the same penalty for everyone
There is a simile I keep coming back to. Put a lump of salt into a small cup of water and the water is undrinkable. Put the same lump into the Ganges and the river is unaffected. The salt has not changed. What changed is what it landed in.
The point being made is that a trifling misdeed may take one person to a terrible destination and be barely noticeable for another — not because the deed was different, but because the two people are. Someone undeveloped in body, virtue and mind is the cup. Someone developed is the river. The same act does not carry a fixed exchange rate.
Which quietly dismantles the ledger picture: there is no table of offences and penalties being applied uniformly, because the medium the action lands in is part of what determines the result. That is also, incidentally, an argument for practice — you are not only avoiding salt, you are widening the river.
And the workings are not auditable
The tradition goes further and puts the precise mechanics off-limits. There is a short list of things described as acinteyya — unconjecturable, not to be speculated about — and the exact ripening of kamma is on it. The stated consequence of trying is not enlightenment but vexation and madness.
I find that a strange and rather freeing thing for a religious text to say. It is the tradition telling you that the causal accounting is real and that you are not equipped to run it. Which rules out the two activities people most want to do with kamma: work out why this happened to me, and work out what somebody else must have done.
So what is actually left to do
Everything the doctrine rules out is retrospective. What it leaves is entirely prospective, and it is small enough to act on: the intention forming right now, which is the only part of the chain you are ever standing next to.
The reflection the texts offer isn't a calculation, it's an acknowledgement of ownership — I am the owner of my actions, heir to my actions, born of them, related to them, supported by them; whatever I do, good or bad, I will be heir to that. Notice what it doesn't contain. No estimate of the balance. No guess at timing. Just: this is mine, and it is coming with me.
That is a heavier claim than the ledger version, not a lighter one. A ledger can at least be reasoned with — you could imagine offsetting, or paying down, or being let off. Ownership offers none of that. But it is also the version that leaves the work in the one place I can reach it, which is the reason I believed some form of this before I knew the tradition existed, and the reason the tradition sharpened it rather than talked me out of it.
None of which settles the harder questions — what ripens when, or across what — and I have written elsewhere about where I am still reading on that. This narrower part I do feel settled on: intention is the thing, it belongs to whoever intended it, and the past is not the place where any of it can be dealt with.