 Mill’s arguments occur in his well-known political essay On Liberty, (Mill 1859) rather than in the context of his logical and methodological writings, but he makes it clear that they are to apply to any kind of knowledge or truth claim. Mill argues from the fallibility of human knowers to the necessity of unobstructed opportunity for and practice of the critical discussion of ideas. Only such critical discussion can assure us of the justifiability of the (true) beliefs we do have and can help us avoid falsity or the partiality of belief or opinion framed in the context of just one point of view. Critical interaction maintains the freshness of our reasons and is instrumental in the improvement of both the content and the reasons of our beliefs. The achievement of knowledge, then, is a social or collective, not an individual, matter.