What Must, Ought, Is Worth and May Not Be Done

The Praxis model of reasons for action takes choice among alternative courses of action to be a matter of what must, ought, is worth and may not be done. It envisages practical decision making systems being given their reasons for action as requirements, duties, rules of valuation, proscriptions and contingent circumstances in a knowledge base. The model’s principles of selection and automated deduction then elicit from them what is to be done. Starting from local circumstances and rules specifying what must or ought to be done in various eventualities, initial options for consideration are deduced. Means end reasoning refines them into practicable alternatives. Alternatives to actions which must be done or actions entailing proscribed activity are excluded. Remaining alternatives are classified along incommensurable dimensions of value specified by relevance principles to bear on the decision context. Choice among alternatives is made using selection rules like the dominance principle. It states that alternatives that are more valuable in one way and no less valuable in any other are better ones. If one is better than any other, it is selected. If not then recourse is made to default selection rules. They provide reasonable ways for resolving conflicting rankings of alternatives along incommensurable value dimensions, for discriminating among indifferent alternatives, or for weakening conflicting requirements so that forbidden options become choosable.