I have assumed permission (from I know not what authority - perhaps the Rene Descartes school of thinkers) to borrow the (in-?)famous postulate "Cogito Ergo Sum" and modify it with a quick-and-dirty Latin twist (Latin as in the language of ancient Rome; the phrase 'quick-and-dirty Latin twist' is not a reference to the salsa) - my own pseudo-Latin concoction: 'Cognito'. Having put that up-front, I feel less morally burdened and free to proceed with my prosaic pronouncements propounding my profound proposition (which the cognoscenti may find confoundingly contrarian).
So let me present the prose (and you can identify the con's yourself). First let me translate the Cartesian premise which I have liberally re-cast in improvised Latin: "I am cognizant of my ego, therefore, I am". Here, 'ego' is defined as: "the boundary of my being, that which defines me as separate from other things, and which contains me". Having paraphrased it thus, let me proceed with my thesis. I submit that the only true verification of 'my' existence stems from consciousness of the fact that there is a 'me' distinct from the universal continuum of energy, matter and various sentient beings (which I recognize as the rest of the universe - 'I' vs. 'The Other'). It starts with my being aware of the universe (of which, it turns out later, I am an integral part), and then being aware of the awareness of the universe (i.e. of the fact that there exists a being who is aware of the universe), and ends with my awareness of a such being, which I recognize as me. The observer observing the observed, and then the observer observing the observer as the observed.
(Phew! If you've had enough of this mind-bending B.S. you should stop reading this post - NOW! and jump to my post on Paris Hilton which you may find far more interesting.)
I am thus able to draw a line where the rest of the universe stops and I start (going from the outside in) or, seen differently, where I stop and the rest of the universe starts (going from the inside out). That line defines the contours of my being ... of me ... of my ego. The moment I am conscious of my existence as distinct from everything else, I have asserted my self, assumed responsibility for my existence and taken pride in myself. I have broken away from the universe and introduced a discontinuity in the (erstwhile) continuum. I am banished from the Kingdom of God. This is my fall from Grace - separating myself from Him, I have become a stand-alone power to reckon with, albeit not comparable with Him. I'm an outsider struggling with the 'other', such is my existential crisis. I am Science analysing Creation and Nature, trying to understand that which I could have known, being part of it - that which I already knew till I saw myself as being outside of it and wanted to understand objectively, as an object. So, from nothing, we got something, and then along came another thing. We now have a duality of I and the Other.
The beauty about duality is that it gives great pleasure in negating itself to make way for singularity. The joy of recognizing oneself as one removed from the other, and then transcending that to achieve one-ness with the other, again, is tremendous. It is embodied in the fusion of charged bodies, which start out being wholly complete and distinct entities, but for an instant of blissfully ecstatic communion, become one through union. And then become two again, in the harmony of opposites. If they were always one to start with, where would that intense joy come from?
So finally, through the awareness of duality yielding to singularity, we become aware of the duality of: (a) duality and (b) singularity, together, as a singular truism. Consciousness of the I and the Other as being part of the same continuum, the I as distinct from the Other and yet a part of it. With the harmony of opposites, the plane of harmony itself as unity.
This is as good as it gets, from what I know and have learned up until now in my life, about the ontology of existence. If you know more and/or better, I would love to hear about it.