Heuristic is a central concept of Lakatos' philosophy both in his early works and in his later work, the methodology of scientific research programs (MSRP). The term itself, however, went through significant change of meaning. In this paper I study this change and the 'metaphysical' commitments behind it. In order to do so, I turn to his mathematical heuristic elaborated in Proofs and Refutations. I aim to show the dialogical character of mathematical knowledge in his account, which can open a door to hermeneutic studies of mathematical practice.