From Ludwig von Mises:
Science does not give us absolute and final certainty. It only gives us assurance within the limits of our mental abilities and the prevailing state of scientific thought. A scientific system is but one station in an endlessly progressing search for knowledge. It is necessarily affected by the insufficiency inherent in every human effort. But to acknowledge these facts does not mean the present-day economics is backward. It merely means that economics is a living thing–and to live implies both imperfection and change.