Equivalent Formulations of Zorn's Lemma and Other Maximum Principles

In this paper, we give a result that maximum principles including Zorn's lemma can be regarded as various types of fixed point theorems. Our main application is that the well-known ordering principles in nonlinear analysis including the Bishop-Phelps argument and a number of its generalizations can be converted to fixed point theorems and vice versa. Consequently, we obtain new results and unify many known results.