ABSTRACT Arne Naess once called himself ?a kind of metaphysician?: did or did he not therewith turn his back on his philosophical mentors in the Vienna Circle? To try to determine the meaning of this self-ascription, this paper first considers in detail two works in which his disagreements with the philosophers of the Vienna Circle found their clearest and most detailed expression. Concentrating on Carnap it will be argued that while some of Naess's criticisms cannot be taken as authoritative, he (...) did indicate a clear dividing line between himself and Carnap. Turning then to Naess's valediction to philosophy of science from 1972, Naess's appreciation of the role of metaphysics for science will be discussed and compared with his appreciation for the role of metaphysics for personal and political life as expressed in his still later ecophilosophy. Once allowance is made for the different needs addressed by his writings for the deep ecology movement and a certain 1960s' rhetoric is discounted as no longer appropriate, it can be seen that Naess's theoretical philosophy exhibited a remarkable continuity throughout. (shrink)