Object Constancy
The separation-individuation process leads ultimately to the
development of the ego as a structure. Its final phase is that
of object constancy, when the ego is formed and established as
a permanent existence, separate from the environment (mother),
and other people are seen to have separate existences. Finally,
the ego is structured and developed, and the child permanently
experiences himself as having a separate identity. (Essence, pg
160)

Object constancy is usually defined as the capacity to see
and relate to the other as a person in his or her own right.
This capacity is part of the quality of the Personal Essence,
of being personal and able to make direct personal contact. (The
Pearl Beyond Price)

Object relations theory contends that object love, which is
love for a separate and differentiated human person, does not
develop until object constancy is attained. In fact, it is part
of the definition of object constancy that when it is achieved
the individual has the capacity to love another as an individual
in his or her own right. (The Pearl Beyond Price)