Every content can be chased down to its initial moment in which it is always found to be preceded by a context, or frame, or clearing which need not themselves be definite contents. The context for a content might be only the sheaf of possible ways for that content to be, an indefinite comprehended plurality. If you bring it to attention it reveals a further even more primitive context, or pretext for a staging. This is what experience no matter how direct shares with thoughts no matter how abstract and distinct; they are because their place has already been prepared. This can't lead to an infinite regress, at some point there must be a possibility of a content that has nothing behind it, that gives birth to itself out of pure emptiness, pure vacuum. This is miles behind what you know as consciousness, but the strange inner urge in consciousness is to swim upstream to that very brink, its origin and finality.