naturalist. Science
must characterize the difference between those two and we pointed once
before to the only fundamental difference. Physical objects are those
which are possible objects of awareness for every subject; psychical
objects are those which are possible objects of awareness for one
subject only. The tree which I see is as physical tree object for every
man, it is the same tree which you and I see; my psychical perception of
the tree is object for one subject only. My perception can never be your
perception. Our perceptions may agree but each has his own. As to the
physical objects, we can entirely abstract from such reference to the
subjects. We say simply: the tree exists or is part of nature; and only
the philosopher is aware that we silently mean by it that it exists for
every subject and that it is therefore not necessary to refer to any
particular subject. But the perception of the tree which is either your
idea or my idea evidently gets its existence only if it is referred and
attached to a particular subject which is aware of it. Such subject of
awareness is that which the psychologist calls consciousness and all the
ideas and volitions and emotions and sensations and images which make up
the mental life are then contents of the consciousness or objects of the
consciousness. To have psychical existence at all means thus to be
object of awareness for a consciousness. Something psychical which
simply exists but is not object of consciousness is therefore an inner
contradiction. Consciousness is the presupposition for the existence of
the psychical objects. Psychical objects which enjoy their existence
below consciousness are thus as impossible as a wooden piece of iron.

If consciousness is nothing but the subject of awareness for the
individual objects, we see at once certain consequences which are too
often forgotten in the popular, haphazard psychology. In the scientific
system of psychology, consciousness has for instance nothing whatever to
perform, that is, consciousness itself is in no way active. The active
personality of real life has been left behind and has itself been
transformed into that self which is merely content of consciousness. The
person who acts and performs the deeds of our life is then only a
central content of our consciousness which is crystallized about the
idea of our organism. It has thus become one of the contents of which
consciousness itself is passively aware. Consciousn