The constitutionalist debate - over where decision-making power in society should lie, and how it should be exercised - is one which is of fundamental importance not only in academia and constitutional theory, but in society generally. The main aim of this thesis is to critically examine the current debate from a particular, sceptical philosophical perspective - one which questions the possibility of convincingly defending moral premises. This controversial perspective, which goes to the heart of debates over moral realism, objectivity, (...) and epistemology is set out and defended in detail, drawing on the work of the sceptical and strongly anti-foundationalist legal theorist, Arthur Leff, and the pragmatic philosophy of Richard Rorty. Some implications of this perspective for the constitutionalist debate and key approaches within it are then considered in the rest of the thesis . This examination includes instrumentalist arguments and "democratic" arguments often relied on by various sides in the debate. It is argued that, when taken to their underlying premises and assumptions, each approach is misguided from the perspective defended here and, therefore, that the current constitutionalist debate is unsatisfactory. Some suggestions of the way forward following this argument are then made. (shrink)