The causes of affinity are very complex, so the Buddha grouped them into four categories to facilitate understanding.

The first is to repay kindness, the second is to exact revenge, the third is to collect debts, and the fourth is to repay debts. Any of these four kinds of affinity exist among the members of a family, or else they would not become family. One also has one or more of these four kinds of affinity with those one interacts with during one’s lifetime.

The difference is how strong or weak the affinity is. Those who share a strong affinity become family members. If the affinity is not so strong, they become relatives or friends. If the affinity is weak, they become acquaintances. If the affinity is very weak, they may just pass each other on the street, and nod and smile at each other.

If they have no affinity at all, they would not even nod or smile at each other. One also has an affinity with someone who may glare at one, but this affinity is very weak. One may encounter this person only once in the entire lifetime.

Ancient Chinese often said that if you have an affinity with someone, you will travel thousands of miles to meet each other, but if you have no affinity with that person, you may not look at each other even when you come face to face.

If you have been kind to someone in past lifetimes, in this lifetime, this person would be very kind to you. When you are in trouble, he or she will help you wholeheartedly to repay kindness.

If someone takes a dislike to you and often insults and slanders you, and even harms you, this person is taking revenge on you.

If someone defrauds or robs you of your money or belongings, this person is collecting debts from you.

If someone helps you make money so that you can be well off financially, this person is repaying debts to you.

The examples of causality, of cause and effect relationships in the four basic kinds of affinities are numerous, but we can see the general idea—we need to nurture good relationships and resolve enmities.

~ Based on Ven. Master Chin Kung's 2003 lecture series on the Amitabha Sutra