Is it not the case that, in just the same way that the notion of "the First World War" only makes sense in relation to "the Second World War", so it is that the notion of "indirect perception" only makes sense in relation to the notion of "direct perception". Now, if that's right, what is this direct perception of which you speak. Conversely, what is this indirect perception? If either term can only be defined with reference to the other what do the modifiers "direct" and "indirect" point to?