The distinction between what is subjective in perception and what is objective is often thought to be that the objective is "real" while the subjective is "illusion". But really, as has been known since Parmenides, the subjective must be every bit as real as the objective. For what is subjective exists as subjectivity and therefore exists in reality. A hallucination, strictly speaking, is just as real as true sight. The difference is that a hallucination is a phenomenon having its being in the brain, and not outside the brain or in front of the face of the one who hallucinates. Hallucinations and dreams are real, every bit as real as true sight; the difference between these and true sight not being that one is real and the other not real. Rather, the difference between hallucinations and true sight is that the first misleads the subject into misinterpretation and false beliefs, while the other (true sight) leads the subject to true knowledge.
Analysis
Thus, we may consider that the difference between subjectivity and objectivity is in this sense: it is that the subjective is what men and women may disagree about with no means of determining who is right, with the various contrary opinions all valid once they are sufficiently close to the mark. The objective, on the other hand, is what men and women will not disagree about; or, if they do, there is a way of determining who is right and who is wrong with complete accuracy, contrary opinions not all being valid (Ratcliffe, 2002).
A telling and popularly known experiment dealing with subjectivity and objectivity is found in those ink drawings that can be seen as representing one or the other of two images. If one looks at the picture ...