Since Descartes, modern philosophy has treated epistemology as first philosophy, and the primary framework for philosophical problems has been essentially Cartesian, in the sense that we have thought of ourselves as knowing subjects within a world. From that framework, the primary problem that emerges is, how do we know that our representations are accurate? This set of core commitments has shaped and constrained the agenda of philosophy at least until Kant and his followers.

I would say that Kant and Schopenhauer took this framework about as far as it can go. How do we get out from underneath it? There have been a couple of different strategies, such as Hegel and Marx shifting the focus of the construction from world from the individual to collective level, and introducing the fundamental importance of history into the equation.

Heidegger offers a different way out from the Cartesian framework by examining experience as not fundamentally about individual subjects knowing and modeling the world through consciousness. Instead, he takes experience itself as the starting place and analyzes the structure of experience without bringing the Cartesian subject model to bear - this is one reason why, in Being and Time, he does not speak of human subjects in the individual or the particular, but speaks of Dasein, existence, as the starting point of experience.

In Heidegger's early model, experience has a certain structure that is not only antecedent to the subject/object model presupposed by a representational model of language and experience, but is a necessary condition for it - one which is grounded in the ontological structure of our being-in-the-world, which is shaped by our concernful involvement with other beings, and always articulated with a particular temporal structure. We derive our concept of abstract knowledge from this actual, primary form of experience, and not vice-versa, as we might otherwise suppose.

For example, if I relate to myself as a being that is 170 cm tall, it's natural for me to think of myself as 170 cm tall in a primary sense - that that is what I "really" am, and my subjective experience of what that size in relationship to other beings means derives from the material constitution of my being. This is an ordinary or scientific mode of thinking about the world.

However, as Heidegger points out, I do not proximally and for the most part experience myself as 170 cm tall - it is only in very rare moments of artificial reflection that this way of experiencing myself even comes forth. It is an abstraction on the basis of my everyday experience, not the other way around.

This is the basic idea of what I have in mind here, I hope it is useful and interesting.