The availability of Piero Sraffa’s unpublished manuscripts and correspondence at Trinity College Library, Cambridge, has made it possible to begin to set out a more complete account of Sraffa’s philosophical thinking than previously could be done with only his published materials and the few comments and suggestions made by others about his ideas, especially in connection with their possible impact on Ludwig Wittgenstein’s later thinking. This makes a direct rather than indirect examination of Sraffa’s philosophical thinking possible, and also shifts the focus from his relationship to Wittgenstein to his own thinking per se. I suggest that the previous focus, necessary as it may have been prior to the availability of the unpublished materials, involved some distortion of Sraffa’s thinking by virtue of its framing in terms of Wittgenstein’s concerns as reflected in the concerns of scholars primarily interested in the change in the his thinking. This paper seeks to locate these early convictions in this historical context, and then go on to treat the development of Sraffa’s philosophical thinking as a process beginning from this point, arguing that his thinking underwent one significant shift around 1931, but still retained its early key assumptions. Thus the approach I will take to Sraffa’s philosophical thinking is to explain it as a process of development largely within a single framework defined by his view of how modern science determines the scope and limits upon economic theorizing.