The one thing I know for certain is that I exist.
Accepted.
And I am able to perceive, and formulate meanings to what is perceived.
Probably, yes.
Many people take their existence, perception and ability to formulate meaning for granted, as though it is a perfectly natural thing, but these basic realities are not explained through our perception.
They do. However, a number of people have examined that capacity throughout history, in isolation and in comparison to other animals, and it seems that it's a more complex iteration of a capacity that's widespread throughout the animal kingdom. As to whether it's 'perfectly natural' or not, that would require some sort of explanation of something about human capacity which was 'not natural', which makes no sense.
Our ability to attach meaning to what we perceive is essentially subjective and does not lead to absolute truth. Our perception is also limited to what can be detected by our physical senses, and it may well be only a small fraction of what exists in reality.
Absolutely.
Science is in effect the human attempt to attach meaning to what we are able to perceive, so it is limited by its subjective nature and can never be defined as an absolute truth.
Actually, science is a methodology specifically designed to try to eliminate that human subjectivity of understanding - nothing can eliminate the subjectivity of the nature of perception, of course. That said, yes, scientific findings are always provisional.
Your assumption that we comprise of billions of cohabiting microbes (and nothing else) in effect contradicts my most basic starting point of reality that I exist in a single entity of perception.
No, it's just a different way of looking at things. We are solid, however a different analysis shows that the individual atoms of which our cells are comprised are mostly empty space. A wall is a single object, yet it comprises a number of bricks which are single objects, yet they comprise atoms... and so on. Nature is a continuum, and in order to study and analyse we fix concepts at given levels of complexity to work within a given context. That neither invalidates the findings that work generates nor invalidates the reality that we can look at any given situation from a number of perspectives.
Life is many things, but it can rarely be said to be simple.
O.