Atom

Atoms can be transparent or opaque. Opaque atoms are atoms in languages where the logical truth depends solely on the external validity of the atom. Transparent atoms have an internal structure that may determine the logical truth of any propositions.

The usual way to express the internal structure of an atom is to apply the Subject-Predicate form to the atom.

Propositional Languages can have opaque or transparent atoms.

First Order Languages use transparent atoms.