  Suppose that I have a yellow, green and purple striped mental image. We may also introduce the philosophical term ‘sense datum’ to cover the case of seeing or seeming to see something yellow, green and purple: we say that we have a yellow, green and purple sense datum. That is I would see or seem to see, for example, a flag or an array of lamps which is green, yellow and purple striped. Suppose also, as seems plausible, that there is nothing yellow, green and purple striped in the brain. Thus it is important for identity theorists to say (as indeed they have done) that sense data and images are not part of the furniture of the world. ‘I have a green sense datum’ is really just a way of saying that I see or seem to see something that really is green. This move should not be seen as merely an ad hoc device, since Ryle and J.L. Austin, in effect Wittgenstein, and others had provided arguments, as when Ryle argued that mental images were not a sort of ghostly picture postcard. Place characterised the fallacy of thinking that when we perceive something green we are perceiving something green in the mind as ‘the phenomenological fallacy’. He characterizes this fallacy (Place 1956):