The difference between what is really present physically (physical or objective reality) and what we actually experience mentally (subjective or phenomenal reality) has been an issue at least since the early greeks. Some accept naive realism,saying that what we experience mentally is exactly the same as what is present physically. Many others,however,say that at least something is lost or gained in the translation from physical to phenomenal experience. A discrepancy between the two types of experience can exist if the sense receptors can respond only partially to what is physically present.