Social Epistemology arose from the recognition that nearly all that we believe or claim to know is second hand and derived from the speech or writing of others. The “we” of “our knowledge” here is, of course, “educated members of advanced industrial societies”. Our remoter, but still identifiably, human ancestors, without speech or writing, picked up such knowledge or belief as they had on their own, apart from what they may have leant from the reactions of others to the presence of quarry or danger. Palaeolithic man, having mastered speech, had access to plenty of second hand knowledge. But it was only of what the people he directly met could tell him. With writing a vast new range of informants is brought into play. Clay tablets and papyrus rolls give way to codices – in other words, books – and another gigantic step forward is made with the invention of printing. We would appear to be going through a comparable information revolution at the present day. We, as defined above, either posses or have ready access to a vast assemblage of common knowledge, actual or claimed. How are we to rationally to decide how much of this we are to accept? It is obviously not all worthy, or equally worthy of acceptance.