I tried to examine the issue in some depth here. While there is no absolute consensus on the issue - and it would nonetheless be quite difficult to give an exact measure of this complex and shifting balance - I would argue that Mussolini experienced a "real" trajectory and evolution of his thought across the intervention, Great War and immediate post war stage. At the same time, given the traits of the Italian socialist movement in the late XIX and early XX Century, I would be wary of comparing Mussolini to an abstract idea of "orthodox socialism". While orthodoxy - or so called "intransigentism" - was a significant portion of a socialist leader's public persona (except, it goes without saying, for the reformers or self-admitted revisionists), it was always in large part a form of "literary orthodoxy", an adherence to a Marxist formal ideal, rather than a deeper commitment to Marx's economical and political principles (which had, anyways, entered Italy in an already "contaminated" form). As a consequence, Marxist orthodoxy was often taken as a synonim of "revolutionarism" and of uncompromising stances with regards to social and class collaboration. From this point of view, while Mussolini was quite openly discussing revisionist positions of syndicalist imprint, as well as welcoming neo-idealist influences from the group of La Voce, he was generally regarded as an expression of a new "intransigent" generation, and his orthodoxy disputed mostly by the old guard.