The category of this question is a matter of necessity, as I could not find a more suitable one (i.e. it does not concern beginners only).
I have tried to make some kind of sense out of the idea of karma, as understood by the generality of Buddhists, Hindus etc. It takes one into a complicated path of reasoning, and I have become a bit sceptical about the possibility of Joe Soap or Mary Brown paying for something that was perpetrated a few lifetimes ago, in this or a later life. These kinds of assertions may be true, of course, but I don't know, and can't make any ultimate sense of them. Of course, whether one believes in karma or not, it is obvious that, if one follows a certain bent, whether it is to slip into drunkenness or some other vice (or, on the contrary, a path of aspiration and effort to improve the tone of one's life), there will be natural consequences. They will be printed, as it were, onto one's relationships and into one's nervous structure, etc. and these consequences will be unavoidable. However, if one makes a single (maybe a big) slip, I cannot see how this will be recorded, for all time, into the "Akashic Records". If, after making the slip, you say, hey, that wasn't so good — I really must try to avoid doing that again, it seems to me that there is a chance of not having to pay for it, since one has learned a lesson from it immediately. I mean, suppose a young man found himself drawn into a plot, with others, to rob a bank. The hold-up is successful, and they get away with the money. Years pass. The man, now much older, has given away his share of the money because of a bad conscience after the event. True, one consequence is that he will always need to be looking over his shoulder, but justice might not catch up with him. Are we to understand that some cosmic Record Keeper has entered the deed in a big, black book, and that, in some future life, maybe, the inheritor of his deed (karma) will, in some future life, have to pay for it in some way?
Years ago, I read a book by Nolan Pliny Jacobson, called: Buddhism, the Religion of Analysis. In it, the author quotes a statement by the Buddha (recorded in Nikaya something or other), in which the Buddha is reported to have said: "I do not teach a doctrine of karma (the common Hindu assumption was that there is karma, in the way most Buddhists understand it), because karma requires justice, and justice is not it". This seems to chime, in my mind, with a statement of a Zen practitioner, who said: "They told us that we were going to Hell, but lo, here is the lotus, opening its blossoms for me to fall on!" — or something very much in that vein.
Several months ago, I came across a Tibetan Buddhist website (the address of which, I failed to note down, and which I cannot now find). On this website, some writer or other said that most Buddhist communities use the teaching of karma as a useful tool, which keeps people mindful of what they are doing, but which, in reality, is not true. I don't know, of course, what qualifications this writer had, that enabled him to make such a statement. However, it certainly rings a bell with me. The old teaching about Hell Fire was a similar tool. It did tend to keep many on the straight and narrow, but, to many more, it also must have caused a good deal of mental anguish. As far as I am concerned, I should want to try to live a decent life whether there is any karma, hell, or not. If this is aspiration is not cherished, one fails to even have a chance of realising one's human potential (even as a secular humanist). It's rather like one's taste in music. One is quite entitled to listen to rubbishy noise that, with the masses, passes for music. However, one has only to be attentive, and one knows what music is, and what is not!
With the teaching of karma, there is an associated problem, and it is not so easily dispelled.
If there is karma, in whatever sense it may be true, (like, despite the fact that there is no continuing identity, "I" will reap the fruits, painful or pleasant, of what is done in my life now), then one has a slight basis for believing that things might slowly get better (despite the teaching that, just round the corner — i.e. in the very next life — there will be a HUGE debt of suffering to pay, for something that "I" did when, for example, "I" was a member of the hordes of Ghengis Khan). However, if karma is just a belief, and has no basis in reality, then there is the frightful prospect that, at death, when my present persona dissolves forever, the next conscious moment MIGHT be one of seeing the fire of Moloch a few feet away, before my body is hurled into the furnace. After all, when I die, babies will be born, and they will all feel that they are "I".
If you go into this, it seems to end up all the same, really, inasmuch as, even if there is karma to pay off, Moloch's furnace might be my next payment off of my debt. It had been sitting there for thirty centuries, and now, instead of, as in my present life, my being a reasonably affluent suburban white person, there might be a dramatic change of culture and time, etc. Karma or no karma, then, the potential for one's next life is like that afforded by a lottery ticket.
With the best will in the world, and with due respect to that great institution, the Buddhist Sangha, a mere belief in karma does raise difficulties. It just does not seem to be enough, to submit to spiritual authority in the matter of karma.
Partly, in all of the above, I have been thinking aloud. I offer my apologies for any inconsistencies that might have been revealed. Nevertheless, if someone, with a clearer mind than mine, would like to respond or to offer any comments whatever on this subject, I should be very interested in what they may have to say. Thanks in anticipation!