 The same argument can be run against the psychologistic conflation of 3-ideas with 3: you might doubt that there really is such a thing as the number 3, existing objectively and independently of us, but you should not for that reason claim that your idea of 3 is 3, for that is just a confusion — it is like saying that your idea of Pegasus is Pegasus, or that your idea of the Parthenon is the Parthenon.