The explanation

1. of the first of these three rules is that like attracts like; a sympathetic person is naturally drawn towards a loving person.
2. The explanation of the second rule is that the one has certain heart qualities and the other has other heart qualities; the qualities of the one supplement those of the other; together, therefore, they make a complete heart; that is why they are drawn together. One will often see two people of quite different qualities who are yet great friends.