The Law of Complementation is closely connected to the former law. According to that law opposite poles of the same type attract when matured - the positive and negative poles, male and female, man and woman because they form together a perfect unit. Therefore, the first prerequisite of the Law of Complementation is the presence of homogeneous species. For example, cock and hen can breed together. However, cock and cat will not breed because they are not of the same species. Neither two hens will breed even though they issue from the same species since they lack opposite poles.
Similar rules also apply to the human character. Not the same but heterogeneous traits are complemented to form a unit. If both partners have the same trait - instability their relationship lacks peace and order. Chaos and disharmony predominate. However, if both partners are maximally stable they miss new impulses; they are bored or even they do not realise their limitations.
The most ideal state for a harmonious life creates a couple which complements itself with different attributes but despite this fact it has the same life goals and values.