This is a general principal that some schools of thought use when they think about how to design a community or government. Generally the principal is preferred by "republican" in the old sense or egalitarian schools.
The idea is that you don't want any entity or small group of entities to have lots of power.
For instance, you don't want a king. You don't want a GodKing. You don't want an army which also governs. You don't want monopolies. You want separation of powers into separate branches of government (e.g. the police should not also be the judicial system). You don't want vast inequalities of wealth or income.
Note that there are other justifications for each of these, sometimes stronger ones.
- If no one faction is too strong, then they all must compromise with each other. Therefore, everyone has some leverage with which to protect themselves from others.
- There is always a way to prevent a powerful party from doing something which is regarded as truly insane or horrible by everyone else.
- If there is a ConcentrationOfPower, the holder of power will possibly be able to modify even the structure of the law-making process. So, a system with protective hard limits such as a Bill of Rights may not be effective unless the system also manages to AvoidConcentrationsOfPower.
- More fundamentally, any system of law-making may fail if a faction accumulates a sufficient concentration of power to alter the system.
- Hard to get things done efficiently, especially reform. Because no faction is powerful enough to ram things through which are very against the wishes of the others, it takes a lot of agreement to do anything. But there will almost always be some party benefiting from the status quo, hence there will often be an opponent to any proposed reform.
Some more radical schools of thought say, when possible, simply AvoidAllPower?
The AvoidConcentrationsOfPower people would probably agree with the spirit behind that, but would say that it is almost never practical.
When power is concentrated at the top of some hierarchy, a movement to AvoidConcentrationsOfPower becomes equivalent to DevolvePower.
See also ConcentrationOfPower
See also PowerLawDistribution, a mathematical formula that models certain kinds of concentrations of power.