Question: How do I convince someone that there is the cause and effect of karma?
Answer: This is a question you can ask… If he/she does not believe in cause and effect, why does he/she not rob in broad daylight? Obviously, this is because such causes can lead to the effects of being caught and punished. This too is the law of karma at play. And the fact that these misdeeds are not done means there is belief in the workings of karma.
Cause and effect beyond such obvious examples might be harder to believe as they are not seen, but the law of cause and effect still operates. For example, a thief who believed he got away can still suffer the effect of being caught later, because he did create the cause to be caught. This principle of karma is pervasive to all other matters in this life and from life to life.