Section path_natural_transformation.
Variable C : PreCategory.
Variable D : PreCategory.
Variables F G : Functor C D.

Lemma equiv_sig_natural_transformation
: { CO : forall x, morphism D (F x) (G x)
| forall s d (m : morphism C s d),
CO d o F _1 m = G _1 m o CO s }
<~> NaturalTransformation F G.