Date of Award


Degree Name

Doctor of Philosophy (College of Philosophy and Theology)

Schools and Centres

Philosophy and Theology

First Supervisor

Professor Ian Thompson

Second Supervisor

Associate Professor Anthony Imbrosciano

Third Supervisor

Professor David Neville


Over the last five hundred years, several conceptually incommensurable theories of ethics have been promulgated. For some moral philosophers, this incommensurability is a matter of deep concern because, in complex cases, there is no tradition-independent method for resolving moral conflict. More recently, a new discipline of applied or practical ethics has emerged. Practical ethics attempts to fill the void between rival moral theories by appealing, first, to the role of reason from an impartial observer perspective and, second, to decision making protocols based on moral principles. This ―first generation‖ attempt at codifying practical ethics failed to bridge the incommensurability gap because decisions based on the application of principles turned out to be just as divisive, in complex cases, as decisions made from a theory-centred perspective. This thesis reconstructs and critiques two of the most prominent decision making protocols in practical ethics.

For other philosophers, the diversity that one finds in ethical theory is precisely what a moral agent ought to expect from a complex discipline such as ethics, particularly in a pluralist society. These philosophers argue that the main problem is not that philosophy failed to deliver a unified or standard model of moral deliberation, but that philosophers took so long to appreciate why epistemological certainty is an unrealistic goal for a discipline primarily concerned with human behaviour.

This thesis argues that the moral diversity one finds in a pluralist society requires moral agents to engage in two types of consensus about ethics. First, ethics requires a thin consensus about the teleological imperatives that enable people to live peaceably in the polis. This thin minimalist consensus engages moral agents in a discussion about universals held in common, universals that sustain a civil society, even while its moral agents hold incommensurable views on many other things. A second type of thick consensus is found in the concept of a practice. As defined by Alasdair MacIntyre, a practice is a long-lived coherent human activity consistent with the telos of the whole human life. The concept of a practice can be usefully employed in a pluralist society because it trades on a thick maximalist consensus on the internal goods that sustain the activity. In this context, rational agents who are separated by thick epistemological disagreement can be shown to hold more things in common than is often appreciated.

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