Let me say in advance that I don’t mean to be harsh in rebuking your points here, because I appreciate the way you’ve raised them, however I do think you are very wrong on many fronts, and as such I will probably sound harsh nonetheless…

grounding and respect for physics

This is, I fear, a meaningless statement. “Physics” seeks nobody’s “respect” — the term merely refers to the observation of physical systems and the deduction of underlying mechanics.

What does deserve respect, or perhaps better phrased as simply personal adoption, is the scientific method and the pursuit of verifiable, observable knowledge. And the first, biggest, most important step to embracing that way of thinking is acknowledging your own fallibility, and requiring more than merely the momentary firing of your own senses to believe something is objectively real. It means accepting that a single observation is just that, and an explanation requires more rigorous study.

It means never, ever rushing to the most complex explanation before eliminating the simple ones, and I cannot think of any set of observations — even a howling translucent phantom rattling chains over a crowd of a thousand onlookers — that would not have simpler potential explanations than “the spirits of dead people walk the earth”. Indeed, that statement is not even a valid or meaningful one in the realm of true, verifiable knowledge — not without an explanation of what ‘spirit’ actually means, which is an explanation nobody seems able to offer.

Second, I have had some out of body experiences.

I don’t see the relation. Well, not scientifically — I do understand the cultural relation, which is that a wide variety of non-scientific ideas ranging from ghosts to psychics to cryptozoological creatures to chemtrails have glommed together into a subculture largely because of their rejection by the rational-minded. So really the connection is “these are two things scientists reject”

However, it should be noted that many kinds of out of body experiences (or in-body relocation experiences — see Richard Feynman’s experiments with sensory deprivation) are a known and documented phenomenon. Science does not deny this. The conflict comes when out-of-body experiences supposedly produce results that would prove they are not purely psychological — such as a person seeing an object not visible from the position of their body — which catapults the claim into extraordinary territory, and calls for much greater evidence. No such evidence has been forthcoming.

It is funny, most people who read Castenada skip the boring bit at the end of the first book — of course, that happens to be the bit where he makes it abundantly clear that he in no way believes that anything he experienced was magical or defied physics, and goes into great detail on the concept of “special consensus” as a subjective sociopsychological phenomenon that allows groups to perceive the manifestation of magical beliefs. As for the following books, written after he was hit with unanticipated fame and a widespread misunderstanding of his work, well, I’d be careful about how seriously you take those.

Some say that we use only about 10% of our brains. Some of that has been dis-proven lately, but the fact remains, we don’t use all of it.

Ugh. Let’s nip this one in the bud. The 10% thing is bullshit — it’s not been recently “disproven”, it was never even claimed to begin with, and is in fact a misquoting of a statement by William James, a psychologist making a quip about how most people don’t value intelligence and work on it. It has no grounding or relevance to neurophsyiology or the modern understanding of the brain.

The “fact” does not “remain” that we don’t use all of it — however, the fact does remain that we barely know a damn thing about how it works. It is capable of all manner of things we don’t understand. Now, what do you think is more likely? That the things it is capable of are things like kinesis and extraphsyical experiences, which would not only be surprising about the brain but would actually defy every single observation we’ve ever made about physics, chemistry and biology? Or that the things it is capable of are in fact entirely internal perceptive phenomenon?

That wasn’t actually a question: the latter is more likely. Full stop.

Thirdly, we have actual physics. We all know about the first four dimensions, length, width, height, space/time. What is not as well known is that (I think) Quantam physics necessitates anywhere from 12 to 48 dimensions. Regardless of which number one latches onto, the thought possibilities of what those other dimensions are for is…is…is…not sure what to say here.

Do not try to understand quantum physics in magical ways. As John pointed out, without the math, the best you can get is an imperfect metaphor. Quantum physics contains exciting phrases like “many universes” and “48 dimensions” but those terms are being used at a level of abstraction that is far beyond what you think.

But, at a lower level, you should understand that all math is an abstraction: it is a language for describing patterns, not a thing with any objective reality. And thus when you wonder about what “other dimensions are for” you betray a lack of fundamental understanding. Dimensions do not “exist” — not even the familiar ones of width and height and depth — they are an invented structure by which we describe the observable universe. As we make more detailed observations, we discover behaviours that are not immediately explainable within the artificial framework of dimensions that serves us so well in macro-level physics — and thus, precisely because it is an artificial language invented by us, we can choose to modify its vocabulary, expand its grammar, state “there is now a new dimension” and test to see whether the updated language helps us better describe what we observe. There are no dimensions; they are not real, they are just a description.

But really, if you want to make the case that ghosts exist or may exist, there is a simple starting point: define “ghost” in great detail. Without that, the claim has no meaning.