formal_logic has definitions from the fields of mathematics,logic
[ noun ] (mathematics,logic) any logical system that abstracts the form of statements away from their content in order to establish abstract criteria of consistency and validity

Used in print

(Clement Greenberg, "Collage" in his Art and...)

But the inner , formal_logic of Cubism , as it worked itself out through the collage , had just as much to do with shaping their decision .