Experience

It seems to be clear that we can know nothing which has not entered into us, or our ancestors, by way of experience. Anything which does not appear to relate to Nature as it presents itself to us right now must be built on the basis of direct experience, even if that was at many degrees removed.
It is therefore necessary to relate each stage in our thinking back to Nature as the sole test of the accuracy of thoughts. We must get back to tangible reality. An abstract proposition may be right or wrong, but unless it can be translated into the concrete how do we even know we are talking about the same concept?
Empiricism and scepticism must be the guiding principles of all politicians. We must not trust the truth of any proposition or assertion until it has been tested by experiment.

But in life and in politics we must act. It is not possible to adopt some form of political precautionary principle and be frozen into passivity. We must do the best we can with the limited undrstanding we have from experience, human instinct and Nature. In so far as our understanding is based on stored experience it may speak the truth but how to be sure. And how can we know that a political action will not have unforesen and adverse consequences. of course we cannot know.
Life is too short to test every action for every consequence. It is too short to test the final consequences of even one action. We must follow a set of rules derived from experience, the rules which have worked best. The guide of experience is therefore conservative. In changing the rules we must always act with restraint - we may be wrong.