Rudolf Carnap's first major book, The Logical Structure of the World [Der logische Aufbau der Welt] (2003a [1928]; hereafter referred to as “Aufbau”), is a key work for the understanding of the philosophical movement called “logical positivism” or “logical empiricism”. Like this movement it has suffered a protracted period of misinterpretation, but also profited from a recent renewal of interest. Once regarded as the explicitly phenomenalist completion of Wittgenstein's positivistic-ally misunderstood Tractatus, it is now recognized as an extremely complex work in its own right that continues to be the focus of intense efforts of re-evaluation and reinterpretation. Here the aim is to abstract as much as possible from the wealth of logical details that make up the Aufbau and to uncover the philosophical point of this work and the interpretative debates about it.

Carnap, language constructor: overview of the Aufbau

Carnap pursued the aim uncontroversially ascribed to the Vienna Circle -furnishing an account of the nature of scientific knowledge adequate to the then latest advances – and his own, more recently recognized aim – accounting for the possibility of objective knowledge – by developing constructed languages for scientific disciplines. Importantly, Carnap did not seek to defend the knowledge claim of science by analysing the languages that science actually used. Over the course of his long career, Carnap changed his mind about the nature of the languages appropriate to the representation of scientific theories, but not about the philosophical strategy of providing so-called rational reconstructions of the logico-linguistic frameworks of scientific theories (in place of analysing them in their historically given form). Their point lay in the clear exhibition of the meaning and empirical basis of scientific propositions.