Abstract

Starting from some manuscripts held in Avenarius’ Nachlass, this essay aims at showing how the drafts written between 1880 and 1883 testify Avenarius’ rethinking of the principle of least effort. In these drafts, as well as in the Kritik, Avenarius separates what seem to be the two “souls” of that principle , obtaining, this way, the principle of the minimum amount of variation and the principle of the progressive elimination. At the same time, this change of mind leads Avenarius to a more dynamic conception of the human conservation, less focused on self-preservation and more oriented towards the adaptation to an environment as wide as possible