Introduction The notion of 'Oneness' — that All is One — arises frequently in the mystical literature; in fact, it seems to be a salient characteristic of the mystical experience. It is intriguing and puzzling, since it seems to contradict the undeniable multiplicity of shapes before our eyes. Even the controversial principle of Idealism (that all is consciousness) seems straightforward in comparison. I am still pondering this idea, so I cannot present a complete discussion. Instead, I will copy over a sketch of ideas provided in my Philosophical Outline (which contains a summary of my metaphysics) to whet your appetite:
Finally, I will discuss Monism — the belief that 'All is One' in some sense. Now everybody's mind has just been reduced to the Mind of God. This includes the 'external universe', which according to Idealism is no more than our consciousness of it, matter having been banished from existence. So only the Mind of God exists. If this mind can be shown to be fundamentally a Unity, in some sense, then it follows that All is One.
My ideas regarding Monism are still under development. Although I have believed in Idealism ever since I was a philosophy student in college, I never felt particularly attracted to the concept of Monism until more recently, when I started studying the mystical literature of the world (including Buddhism and Vedanta). There is a very noticeable tendency for mystical writings to take a monistic (as well an idealistic) slant. In fact, Monism is at the core of the Advaita Vedanta, but it is also at least implicit in much of Mahayana. Having reflected on it for a while, I can begin to see reasons why this might be true. I can only sketch a few of these reasons.
To begin with, I will never accept a philosophy that simply denies that I perceive a multitude of shapes and colors when I open my eyes. This much is self-evident, and no reasonable philosophy or religion asks us to be irrational. (Zen may come close, but this is not to deny but rather to transcend ordinary discriminative thinking in order to reach a 'higher state of consciousness'. We will discuss something similar to this when we get to Emptiness.)
Now how might consciousness, with all its multitudinous shapes and colors, be a Unity? Well, for the shapes and colors to be truly distinct, they would have to be in some kind of space, just like the 'external space' of materialism, would they not? And has not this external space been refuted, according to the fundamental principle of idealism? This is not to deny that the shapes and colors appear distinct. But this may just be an illusion in the same sense as external space itself is an illusion.
Furthermore, I have always been intrigued by the fact that consciousness can see many things (or 'pixels') all at once — in an instantaneous 'snapshot' we might say — and form all the details of perception into a single whole. We take this for granted, but upon closer reflection, this aspect of consciousness is not so trivial and is even a bit miraculous. Why don't the 'pixels' of consciousness simply disintegrate into infinitesimal atoms of consciousness? What holds it all together? I can intuitively sense that there is indeed a mysterious essential unity to consciousness, but I cannot yet put my finger on it.
I think that 'mystics' are far more sensitive to this unity of consciousness than ordinary people. In fact, the crystallization of consciousness into a diamond-like unity may be the salient characteristic of the mystical experience. (Actually, this cute metaphor may be quite misleading in some ways. Please take it with a considerable grain of salt.) At some time, I hope to develop these suggestive notions into a more detailed and coherent philosophy.