[bsrhng]

No, 'things outside' are only known to us as mediated through (what we perceive as) the body. The object of which you estimate your degree of belief lies within our experience. There is no sense in which you can say that you know something outside the means of perception. You cannot have degrees of belief about whether you are experiencing something in the first place.

[hackinthebochs]

That our perception mediates our access to the outside world does not undermine our ability to deduce the existence of the outside world. We can't have 100% certainty that the outside world exists, but we don't need 100% certainty for knowledge. The question is which model do we give higher credence to: the one where all the structure inherent in our perception that suggests an external world is coincidental or internally generated, or the model where there actually is an external world and we perceive it through our senses. The latter model is more likely given various criteria, e.g. parsimony.

[bsrhng]

What I'm arguing about is that there is a big assumption made prior to any judgement about models of any kind.

At any given point all you have is your singular experiential point of view -- you're reading this comment, coding, chewing your food, remembering a childhood memory, having sex or whatever. That any of this has any correspondence to anything beyond the fact that you are experiencing it at that moment is an assumption. Only then you might start reasoning about the contents. And the contents are of course subject to any brain-in-a-vat objections you might make.

Obviously you cannot live at all if you start questioning your experience at that level. But the point I'm trying to make is that that singular point of view, whatever you are experiencing, is literally all there is. Nothing ever happens, as far as you (or anyone) is concerned, that is different from a personal experience.

To continue to exist at all of course, I don't think there is any other way than what you describe, to start acting based on whatever it is that you are experiencing. But you have to take that initial step and I think being aware of it can lead to a somewhat different understanding of why you feel what you feel and in particular how culture works.