Synthetic perspectives on the Yoneda lemma
By Emily Riehl
Appears in collection : Synthetic mathematics, logic-affine computation and efficient proof systems / Mathématiques synthétiques, calcul logique affine et systèmes de preuve efficients
The Yoneda lemma, considered to be the fundamental theorem of category theory, is difficult to explain because its statement is both abstract and obscure. But in synthetic category theory, "functionality" and "naturality" are automatic, and the Yoneda lemma can be understood as an "arrow induction" principle that applies in covariant or contravariant settings.
