In this paper we describe the LaTTe proof assistant, a software that promotes the Lisp notation for the formalization of and reasoning about mathematical contents. LaTTe is based on type theory and implemented as a Clojure library with top-level forms for specifying axioms, definitions, theorems and proofs. As a pure library, LaTTe can exploit the advanced interactive coding experience provided by modern development environments. Moreover, LaTTe enables a form of proving in the large by leveraging the Clojar/Maven ecosystem. It also introduces a very simple and concise domain-specific proof language that is deeply rooted in natural deduction proof theory. And when pure logic is not enough, the system allows to take advantage of the host language: a Lisp way to proof automation.