I have always found Karma to be a very interesting principle. Karma is founded on the the belief of causality and ethical consequences.
According to the Wiki, a common theme to theories of karma is its principle of causality. One of the earliest associations of karma to causality occurs in the Brihadaranyaka Upanishad of Hinduism. For example, it states:
Now as a man is like this or like that,
according as he acts and according as he behaves, so will he be;
a man of good acts will become good, a man of bad acts, bad;
he becomes pure by pure deeds, bad by bad deeds;
And here they say that a person consists of desires,
and as is his desire, so is his will;
and as is his will, so is his deed;
and whatever deed he does, that he will reap.
— Brihadaranyaka Upanishad, 7th Century BC
Personally, I have found that those who have done wrong to me have ended up facing less than desirable circumstances from time to time in their lives that bore some similarities to what they did to me or tried to to. Is it karma? Who knows? I do not propose to be a scholar when it comes to topics such as this one, but I will say that the principle is interesting. Obviously it bears resemblance to Biblical Scriptures about “reaping what you sow.” I am curious to know of others who have bore witness to a person who has wronged them going through their own natural consequences OR the other way around. Perhaps there are people who have done wrong to other people who have endured their own circumstances brought on by karma?