In the long-standing debate between positivism and non-positivism, legal validity has always been a subject of controversy. While positivists deny that moral values play any role in the determination of legal validity, non-positivists affirm the opposite thesis. In departing from this narrow point of view, this book focuses on the notion of legal knowledge. Apart from what one takes to constitute the grounds of legal validity, there is a more fundamental issue about cognitive validity: how do we acquire knowledge of whatever is assumed to constitute the elements of legal validity? When the...