9. The same distinction could very easily be shown to be the foundation of every other science. All the physical sciences have this in common, that they are researches into what is real as distinguished from what is apparent, that is, from what lies exposed and obvious on the very surface of things. Perhaps, however, I have said enough to render intelligible the distinction of which I have been speaking. Let me just repeat, that upon whatever object our attention may be directed, no science of that object is possible unless we admit in regard to the object in question, whatever it may be, a distinction between the apparent and the real, the obvious and the hidden; for, as I have already remarked, if the apparent and the real are identical, no science or research is necessary to instruct us in the nature of the object which we may be considering. And let me add this, too, that while science brings before us the real, it at the same time corrects or sets aside the apparent. Astronomy, in teaching us that the earth revolves round the sun, corrects or dislodges the apparent fact of natural observation that the sun revolves round the earth.
10. This distinction between real and apparent, then, being understood, I have now to show you for what purpose I have brought it under your notice, and how it may enable you to understand the position which my system of metaphysics occupies, or professes to occupy, in relation to our antecedent
