ABSTRACT
Theoretical concepts refer to things or characteristics which we humans are unable to perceive with the senses. Theoretical singular terms of the natural sciences, for example, denote individuals that are too small to be seen, from bacteria to molecules, atoms, and subatomic particles. Theoretical general concepts of the natural sciences denote properties or kinds of effects, for the perception of which there is no sense organ at our disposal, for instance electrical or magnetic fields; or they denote inner (chemical, biological, neural) structures of a system, of which we are only able to observe the external input–output relations. In the human and social sciences, singular theoretical terms can stand for complex social structures, e.g. the national state called Germany. Theoretical predicates of these sciences denote for example mental or emotional states of people, or complex conditions of societies.
