who introduced the idea of motive or intent in morality, and Peter Singer who introduced the idea of preference in moral decision-making. Deontological ethics, notions based on 'rules' i.e. that there is an obligation to perform the 'right' action, regardless of actual consequences. This approach is epitomized by Immanuel Kant's notion of the categorical imperative, which was the centre of Kant's ethical theory based on duty. Another key deontological theory is natural law, which was heavily developed by Thomas Aquinas and is an important part of the Catholic Church's teaching on morals. Threshold deontology holds that rules ought to govern up to a point despite adverse consequences; but when the consequences become so dire that they cross a stipulated threshold, consequentialism takes over. Virtue ethics, derived from Aristotle's and Confucius' notions, which asserts that the right action will be that chosen by a suitably 'virtuous' agent. Sometimes, these normative ethical theories clash, which poses challenges when trying to resolve real-world ethical dilemmas. One approach which attempts to overcome the seemingly impossible divide between deontology and utilitarianism (of which the divide is caused by the opposite takings of an absolute and relativist moral view) is case-based reasoning, also known as casuistry. Casuistry does not begin with theory, rather it starts with the immediate facts of a real and concrete case. While casuistry makes use of ethical theory, it does not view ethical theory as the most important feature of moral reasoning. Casuists, like Albert Jonsen and Stephen Toulmin (The Abuse of Casuistry, 1988), challenge the traditional paradigm of applied ethics. Instead of starting from theory and applying theory to a particular case, casuists start with the particular case itself and then ask what morally significant features (including both theory and practical considerations) ought to be considered for that particular case. In their observations of medical ethics committees, Jonsen and Toulmin note that a consensus on particularly problematic moral cases often emerges when participants focus on the facts of the case, rather than on ideology or theory. Thus, a Rabbi, a Catholic priest, and an agnostic might agree that, in this particular case, the best approach is to withhold extraordinary medical care, while disagreeing on the reasons that support their individual positions. By focusing on cases and not on theory, those engaged in moral debate increase the possibility of agreement. Applied ethics was later distinguished from the nascent applied epistemology, which is