ABSTRACT
The alternative theories fall under the following two heads, viz. Inter-subjective and Extra-subjective. According to the first type of theory, the collective character of the hallucination is entirely due to telepathy, and there is no question of there being any kind of extra-subjective entity localized in space, which is the common object of all the correlated quasi-perceptions. According to the second type, telepathy is inadequate to account for the facts, and it is necessary to postulate such an extra-subjective localized common perceptum. Each type of theory can be developed in many different specific forms.
