Schumpeter's first book, Das Wesen und der Hauptinhalt der theoretischen Nationalökonomie, published in 1908 when he was twenty-five, was one of the earliest attempts to give neoclassical economics a methodological foundation. His approach was influenced by the precursors of logical positivism, such as Ernst Mach, Henri Poincaré, and Pierre Duhem. In a historical survey of nineteenth-century positivism David Oldroyd observes:

It was these “isms” that influenced Schumpeter's economic methodology. My argument in this chapter is that Schumpeter's methodology in Wesen can best be interpreted as instrumentalism, that is, the view that theories are not descriptions but instruments for deriving useful results and are neither true nor false. Instrumentalism is the opposite of scientific realism, which asserts that the object of science exists; theory describes it, and therefore it is possible to ask whether a theory is true or false.

A lacuna in the history of economic methodology

Schumpeter's contribution to economic methodology has not received the attention it deserves. There are several reasons for this.