ient of treatment, we can express this
fact by saying that a doctor is essentially the doctor of a patient.
Further, it is true that a recipient of treatment implies a giver of
it, as much as a giver of it implies a recipient. Hence we can truly
say that since a doctor is the doctor of a patient, a patient is the
patient of a doctor, meaning thereby that since that to which a doctor
is relative is a patient, a patient must be similarly relative to a
doctor. There is, however, another statement which can be made
concerning a doctor. We can say that a doctor is a doctor of a human
being who is ill, i. e. a sick man. But in this case we cannot go on
to say that since a doctor is a doctor of a sick man, a sick man
implies or is relative to a doctor. For we mean that the kind of
reality capable of being related to a doctor as his patient is a sick
man; and from this it does not follow that a reality of this kind does
stand in this relation. Doctoring implies a sick man; a sick man does
not imply that some one is treating him. We can only say that since a
doctor is the doctor of a sick man, a sick man implies the possibility
of doctoring. In the former case the terms, viz. 'doctor' and
'patient', are inseparable because they signify the relation in
question in different aspects. The relation is one fact which has two
inseparable 'sides', and, consequently, the terms must be inseparable
which signify the relation respectively from the point of view of the
one side and from the point of view of the other. Neither term
signifies the nature of the elements which can stand in the relation.
In the latter case, however, the terms, viz. 'doctor' and 'sick man',
signify respectively the relation in question (in one aspect), and the
nature of one of the elements capable of entering into it;
consequently they are separable.

Now when it is said that knowledge is essentially knowledge of
reality, the statement is parallel to the assertion that a doctor is
essentially the doctor of a sick man, and not to the assertion that a
doctor is essentially the doctor of a patient. It should mean that
that which is capable of being related to a knower as his object is
something which is or exists; consequently it cannot be said that
since knowledge is of reality, reality must essentially be known. The
parallel to the assertion that a doctor is the doctor of a patient is
the assertion that knowledge is the knowledge of an object; for just
as 'patien