Hello Dave ...
I had to read your post a few times to recollect my thoughts ... In fact I am not even sure where to begin ... your post is so to the point ... and deserves my full coherent response.
You are right, Descartes said, "I think, therefore I am." ... very true ... but I do believe that .... just because I have the ability to create a thought does not mean that I, actually exist ... but then surely this would demand the question: "Who am I"?
My "I" woud have to broken down into segregate parts, like my physical being and my non physical being ...
It is said that the brain is the seat of the mind ... (conscious and subconscious), ... but physically, my brain is nothing more than just matter ... a 3lb organ made up of pure fat compounds, flushed in liquid ... which ... after death ... is incapable of creating a thought... therefore, in light of that, I would have to sustain that it is incapable of creating thoughts whilst I am alive.
We have to agree to disagree with the fact that we cannot create our our reality ... as I believe we can ... A perceived cold chilly air to me ... may seem like a warm summer air to someone else ... so, technically, in fact we have created our own two separate realities ... based on our perceptions.
Of course, I agree, that we all have common realities, we all know what a PC is ... and what it is used for ... but in some remote part of the world a tribesman who has never been exposed to a PC may think it is an alien object which he would, probably define, in accordance to his lack of knowledge and experience with such an object. He may even think it is the devil impersonified .... but then we may all have that feeling from time to time ... hehehe ...but you know what I mean ....
I do believe that you are right ... that we are part of some greater scheme ... not necessarily in a game or supercomputer ..... but ... perhaps in an infinite universal superconscious ... where as you quite rightfully said ... there is no beginning and there is no end ... and I strongly believe that my thought making capacity comes .... not from me ... but from this universal consciousness ... the supremacy of all living matter ....
We are all but energy fields, made up of atoms, neurons and particles various ... so we react, intereact and behave as energy forces in unisom with our environment .... being it too ... an energy force ..... even our eyes can deceive us .. as they are only receptors for reflections of light that determine a "possible" definition of reality.
Could it not be that we live in multiple realities at the same time ... similar to the concept of parallel universes? ... after all ... if I choose X option ... the outcome will be Y ... but if I choose W option, in the same, occupied, space and time ... then the outcome would be Z ... so I have made my own new reality within an existing reality ... and parallel to it ... because I still have the original option of choosing X.
Ok, I have rambled on now and it's not my usual time of day for philosophical thoughts .... I'm ahead of myself ....
Take care and I shall look forward to this debate going further ...
Best wishes
Venerina