Karma is not much different from the biblical notion that you reap what you sow. You might think that as an agnostic I would have a hard time with karma, but I don’t. When we clarify some misconceptions, most of the problems with karma disappear.
Karma means “action” and comes down to cause and effect (technically, karma is cause and vipaka is effect).
Karma only applies to intentional actions. So we’re talking about choices, not fate. This means it’s not karma when a hurricane wrecks your house. Hurricanes don’t act intentionally. And even if you’re a murderer, there’s no cause and effect relationship between you pulling a trigger and the winds over the Gulf of Mexico.
Even if you’re hit by a drunk driver, still there’s no connection between you cheating on your wife and some stranger getting drunk. You just happened to be in the wrong place at the wrong time.
The drunk driver going to jail is karma, though, because there’s a direct cause and effect link between her actions and her stay at the crowbar motel.
So the two biggest mistakes people make about karma are applying it to unintentional actions, and failing to make proper cause and effect connections.
But there’s the objection that sometimes bad people prosper and good people do not. Just as bad luck isn’t always connected to one’s actions, fortunate events too are not always connected to one’s actions. And, even if a bad person is materially well off, it doesn’t mean that person is psychologically well off. Mean people are mean because they’re unhappy. And happy people are happy even when they’re poor.
Many Buddhists believe we owe a cosmic debt to people we’ve wronged. But this is because the momentum of our actions creates a chain of cause and effect, not because of a deity who keeps a list and metes out punishments (note that this differs from some Hindu views on karma). What’s really essential here is that if we’ve hurt someone then we have an ethical obligation to make it up to them as best we can.
As an Agnostic Buddhist, the only difficulty I have with karma is the belief that it can follow you into the next life. If rebirth is true then this makes sense, but as I wrote in my post about rebirth, right now this life is all I have, so I’ll worry about the next life, if there is one, when the time comes. But even if there is no next life, the chain of cause and effect our actions create continues after we die.