However there is no strict definition of the common good for each situation. The good that is common between person A and person B may not be the same as between person A and person C. Thus the common good can often change, although there are some things such as the basic requirements for staying alive: food, water, and shelter - that are always good for all people. Some assert that promoting the common good is the goal of democracy (in the sphere of politics) and socialism (in the sphere of economics).