Transcendental Knowledge?

[Mudhammam]

I wouldn't know how to deny it - but how would I use it to establish that it is fundamental? That's after establishing that it exists, of course.

What about Descartes' famous "je pense, donc je suis"? You can deny the existence of the contents within conscious experience, but you cannot deny the very experience of consciousness itself without contradicting yourself. That being said, as far as the role that mind plays in translating sense data into an intelligible, interactive, objective world that I experience, my question pertains to what extent is it that mind shapes our perceptions (can it be less than all of them?) and where does this leave us in terms of knowledge of an object's nature, as it supposedly exists, independent of a perceiving subject? Or must we plead agnosticism?