A little book which helped me a lot in my metaphysical studies is the Kybalion, By Three Initiates,
you can get this book for free online; here is a link
http://www.hermetics.org/pdf/kybalion.pdf
Read Chapter IV The Divine Paradox and Chapter X Polarity and they may give you some insight into
duality and non-duality, also read some literature on Taoism as the centerpiece of Taoism is about
duality and non-duality. The yin and yang symbol of Taoism is a good example of this. Basically duality
refers to the dual nature of the human mind and how our mind perceives reality which is different than
the spiritual perspective of oneness, wholeness, or non-duality. Duality and non-duality are
metaphysical concepts.
You can understand this in your mind but it will only become clear if you experience it. To see the light
of God in all things is similar to non-duality, but to see all of the differences in this creation, and all of
the labels we attach to those differences, is similar to duality. Human beings have more in common than
we do that is different but the human mind often dwells on the differences which divide us. Both duality
and non-duality serves us; duality is as the mind and non-duality the heart; the middle path is said
to be best.
