[extract] Philosophers and scientists often describe theories, laws, and explanations as
applying to the world at different 'levels'. This idea of a 'level of application' is
often used to demarcate disciplinary or sub-disciplinary boundaries in the sciences.
For instance, stoichiometric laws and quantum mechanical laws might
be said to describe chemical phenomena at different levels. More generally,
the idea of levels is used to distinguish more fundamental laws or theories
from less fundamental ones: more fundamental theories are those that apply
at more fundamental levels.