Philosophical endeavors turn in a constant circle, arriving again at a point where they have already been. Thereupon materials now lying in the dust can perhaps be processed into a magnificent structure.

–Immanuel Kant, 1781
Critique of Pure Reason 

Progress exists only in the realm of what is ultimately unimportant for human existence. Philosophy does not evolve in the sense of progress. Rather, philosophy is an attempt at developing and clarifying the same few problems; philosophy is the independent, free, and thoroughgoing struggle of human existence with the darkness that can break out at any time in that existence. And every clarification opens new abysses.

–Martin Heidegger, 1927
Phenomenological Interpretation of
Kant’s Critique of Pure Reason 

Ultimately we are seeking a better understanding of what it means to be human. In this quest, progress is not made by finding the ‘right answers,’ but by asking meaningful questions — ones that evoke an openness to new ways of being.

–Terry Winograd & Fernando Flores, 1986
Understanding Computers and Cognition:
A New Foundation for Design
Page 13