ABSTRACT
The very sense-data which people treat as evidences of the reality of physical things are deceptively aped by dreams and hallucinations. Taking the conflicting theories as they find them, philosophers may well wonder what exactly it is in which the 'reality' of the external world consists. For the orthodox physicist, reality, as it has been picturesquely put, is a 'mad dance of electrons', and sense-data, for all that they are the physicist's only direct evidence of the existence of any external world whatever, are counted as 'merely mental' and 'subjective'. Mechanism and vitalism compete directly as rival interpretations of the facts of biology. The Eastern doctrines of the senses as spreading a veil of illusion over reality, and of the elaborate ascetic regimen for mind and body by which the student must discipline himself for penetrating to the reality behind the veil, have never profoundly affected the main current of Western thought.
