Simple_Min

Mind is the forerunner of all actions.
All deeds are led by mind.
If one speaks or acts with a corrupt mind,
Dukkha follows,
As the wheel follows the hoof of an ox pulling a cart.

To understand Karma and its effects you need to add a few more words to your mental dictionary. Sukkha (good, what you want) and Dukkha (bad, what is to be eliminated).
(Both are from Indian Sanskrit texts)

As the ideology goes, dukkha results when you do "bad" deeds. You feel bad when you take advantage of someone, for example. That feeling is the result of "bad karma".

You murder someone, and you fear for your own life and what the police will do you for the act. That is karma.

If you are looking at Karma in ways that "Karma is true if and only if I hit someone with a rock and then later I get hit with a rock, " then that is the incorrect way to approach it. (Again, Hinduism and Buddhism have a great and wonderful connection with the cosmos. It is almost as if they are science with mythology mixed in for good measure.)

For example, you cannot prove (qualitatively) gravity exists...and as Dr. Einstein showed with his work in Relativity that gravity is not real. But we feel it and it's dukkha (or sukkha; whichever way you want to look at it)

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