Western secularists have a difficult time accepting kamma, but to me it is one of the most obvious things in the world. In fact, to say that kamma doesn't exist is to say that actions don't have consequences. This is, of course, an absurd view. If you didn't believe that your actions had results, then you wouldn't do anything. In order to get a university degree you need to study, for example. Studying is the cause, and the degree is the result.
Kamma has effects which are both immediate, and have a future component. So, if I go to the fridge to eat some ice cream, then that's kamma. The result is that I experience pleasant sensations here and now (because ice cream is delicious), but I can get fat over the longer term if I eat too much.
It is useful that kammic results often do not happen in isolation. What we usually experience at any moment is the result of lots of kammic actions mixed together. This mixing process, together with the fact that kammas can have effects that extend into the unquantifiable future, means that it is often difficult to foresee what their true consequences are. There's a kind of "law of unintended consequences" in our actions. I think it is our belief that we are exempt from, or mindless of, the future ripening of kamma that causes so much trouble for ourselves and the world. If the results were always and only instant, then I am sure we would commit only good actions. Humans do not think about the longer term implications of their actions, and if they do, they tend to think that they can dodge them.
One of my favourite stories about kamma, and the way good and bad kammas can interact, is the death of Steve Banerjee. You are probably unaware of this, but Steve was an entrepreneur who co-founded the Chippendales, a touring male dance troupe featuring erotic dancing. The Chippendales became famous, and was undoubtedly a huge financial success. So, through hard work, he was able to enjoy money, success, and all of its trappings. However, he went on to make some bad choices. He attempted to hire someone to burn down competing nighclubs. He also attempted to have his business partners murdered. Unfortunately for him, the hitman he hired confessed to the American Embassy. This eventually led to Banerjee's arrest for conspiracy to commit murder, murder for hire, racketeering, and arson. Hours before he was sentenced, he hung himself in his detention cell.
Banerjee used his industriousness to create commercial success. Instead of enjoying its fruits, he let ill-will go to his head and committed all manner of nasty deeds which resulted in him taking his own life. Who would have thought that creating something successful could lead to one's own death? The answer is, clearly, that it can, if you start doing bad things.
Although kammas can have complex interactions when they ripen, so that it is difficult to predict the manner of the results, there is a clear path through all of it. It's actually quite simple: good actions tend to ripen in good results, and bad actions tend to ripen in bad results. So, just do good deeds, and you don't have to worry about the results.
AN 8.40, "Vipaka Sutta: Results" details the results of bad actions. It says that stealing, illicit sex, lying, divisive tale-bearing, harsh speech, frivoulous chattering, or taking intoxicants can lead to hell, realm or ghost realm. In their slightest form, they can have an effect in the human realm. The effect in the human realm is dependent on the action, as follows:
- stealing leads to loss of wealth
- illicit sex leads to rivalry and revenge
- lying leads to one being falsely accused
- divisive tale-bearing leads to the breaking of friendships
- harsh speech leads to unappealing sounds
- frivolous chattering leads to words that aren't worth taking to heart
- intoxicants lead to mental derangement
So, please keep to the five precepts as faithfully as you possibly can.