During discussions with one of my friends (who is an undergraduate biologist) we often enter into the empiricism vs. rationalism debate. In support of empiricism as the best route to true knowledge my friend often cites the many practical achievements made throughout history resulting from a scientific/empirical approach. In response to this I find it difficult to cite any significant advancements or examples of knowledge which can be credited to the side of rationalism. Indeed it seems to me the invocation of science's great 'utility' is often used as a defence of its (sometimes questionable) actions as well as its assumed superiority as a means to true knowledge. Therefore my question is how can one most effectively challenge science's monopoly on truth and knowledge (particularly in today's 'science worshipping society') in the face of its great practical achievements?