This paper compares and contrasts three views on the issue of 'solipsism' that were much discussed in the first half of the 20th century, namely those of Wittgenstein, Carnap and Reichenbach. While the paper deals mainly with early Wittgenstein, the so-called 'later Wittgenstein ' is seen as arguing that Carnap's Aufbau, and any similar 'solipsist' reinterpretation of the language must start with a notion of experience utterly different from the one we actually have. And this criticism actually coheres with Wittgenstein (...) 's views in the Tractatus. (shrink)