Q. About Rationality and Nature

[The Grand Nudger]

I take it on faith that our sense data and cognition have arisen biologically to successfully cope with something real of which we are apart.

I take it on evidence that our sense data and cognition have only developed biologically to deal with the inputs they receive, whether real or simply perceived. Deer, for example, are blind by human standards. Yet they are notoriously skittish of motion (which is pretty much all we think they can see). They have incredibly developed senses of smell and hearing, on the other hand - but how they might know that a certain sound or smell is danger would always fall to post hoc, ergo propter hoc. They react to inputs which could not properly be considered danger, the "danger" is not real, it is perceived, and largely in error (hence skittishness). Nevertheless, their strategy, sense data, and cognition works, apparently- as they are still here. Whats important, clearly, is not whether our sense data and cognition can cope with something real, but whether or not it can handle inputs of any kind; the effect of that "coping" when juxtaposed against what -is- real (as there -is- danger in the world for deer).

The world that we perceive ourselves to be a part of needn't be "real" it just needs to be computationally actionable. "Real" to us. If we -were- "brains in a vat", it wouldn't matter - as our world is simply the operating environment that our equipment affords us regardless. If rational principles work in that environment, it would be rough to try and extend them beyond it (as sho-nuff suggested), and they needn't be thusly extended - though, agreed, we just don't seem to be in a position to know that.