Non-Dualism....

The mind can know as a second thing, as an object, that which is
outside itself. This applies to thoughts also. If it is to know
anything as it really is in itself, it must unite with that object and
become it, in which case the distinction of duality disappears. For
instance, to know a person, one must temporarily become that person by
uniting with him. Otherwise, all one knows of that person is the
mental picture, which may not be similar to the real person.
Similarly, the Ultimate Consciousness is not something to be known as
a second being apart from oneself. If he knows it in that way he
really knows only his mental picture of it. To know it in truth he has
to enter into union with it and then the little ego disappears as a
separate being but remains as part of the larger self. The wave then
knows itself not only as a little wave dancing on the surface of the
ocean, but also as the ocean itself. But as all the water of the ocean
is ONE, it can no longer regard the millions of other waves as being,
from the standpoint of ultimate truth, different from itself. To
render this clearer still, during a dream he sees living men, houses,
animals, and streets. Each is seen as a separate entity. But after he
awakens, he understands that all these individual entities issued
forth from a single source--his own mind. Therefore they were all made
of the same stuff as his mind, they were non-different from it, they
were not other than the mind itself. Similarly when he completes the
Ultimate Path he will awaken from the illusion of world-existence and
know that the entire experience was and is a fragmentation of his own
essential being, which he now will no longer limit to the personal
self, but will expand to its true nature as the universal mind. The
dream will go on all the same because he is still in the flesh, but he
will dream consciously and know exactly what is happening and what
underlies it all. When this happens he cannot go on living just for
purely personal aims but will have to enlarge them to include the
welfare of all beings. This does not mean he will neglect his own
individual welfare, but only that he will keep it in its place side by
side with the welfare of others.

— Notebooks Category 21: Mentalism > Chapter 5: The Key To the
Spiritual World > # 170