US government has a limited power because it cannot do certain things, and specifically it is not allowed to breach certain individual freedoms: so it can be said that the motivation for a limited government is to protect individual freedoms.
See for example the text of the first amendment:
"Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof" - this limits the power of the government so that people have a freedom to practice their religion.
Philosophy is a scientific discipline which includes such questions as
- ethics: how we should behave
-epistemology: what is knowledge, is it subjective, objective, etc
- logics: what logically follows from other facts.
In a way these sub-fields are only loosely connected, but what they have in common is the type of inquiry (logical thinking, argumentation) used. <span />
