In a once-famous article, ‘The Elimination of Metaphysics through the Logical Analysis of Language’, first published in 1932, Rudolf Carnap (1959) wrote:

So presumably Mozart expressed what Spinoza attempted to put into words in the Ethics, and Beethoven conveyed, in his characteristic middle-period works (one takes it) the ‘heroic dualism’ which Descartes senselessly propounded in the Meditations. And Nietzsche is given credit by Carnap for abandoning metaphysics and expounding his world-attitude in poetry in Thus Spoke Zarathustra.

It is a strange, if in some respects gratifying conclusion to Carnap's alleged demonstration of the senselessness of metaphysics. What cannot be said, because it has no ‘cognitive significance,’ can be, pace Ramsey, composed, either as music or poetry. But one's pleasure at the recognition by a hard-nosed logical positivist that music (and I'd rather leave Zarathustra out of it) can express attitudes to life is modified by unease about how Carnap or anyone else can know what Spinoza or Descartes were trying to say in their metaphysical works if they were devoid of meaning.