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Can one derive an 'ought' from an 'is'?
The problem with deriving an 'ought' from an 'is' comes from the alleged logical distinction between statements of fact and statements of value. The distinction has led many philosophers to claim that a descriptive statement can never entail an evaluative statement. The question can be approached from the point of view of someone who believes in objective moral truths or from the point of view of someone who believes that ethical statements only have subjective truth (where for the former, morals are absolute, and for the latter, morals are relative); therefore I am going to divide the possible reactions to the question into four broad categories outlined as follows. (The categories are broad in that each category still contains various options - however, for the two objectivist reactions I have given examples of specific philosophers who embody those views, namely Moore and Searle.) 1) I am an objectivist and I believe that you cannot derive an 'ought' from an 'is' "I believe that there are such things as ethical truths and that they are logically distinct from facts in the sense that you cannot derive an ethical statement from a factual statement or define ethical terms in terms of non-ethical terms. N.B. the 'ought's in ethical statements are categorical 'ought's." An example of a philosopher who holds this kind of view is Moore. He believes that the term 'good' is indefinable. Anyone who tries to derive an 'ought' from an 'is' is committing the 'naturalistic fallacy', in that they are trying to define 'good' in terms of something entirely distinct - or indeed trying to define good at all. Moore uses the analogy of the colour yellow to explain the indefinability of 'good': you can point to things that are yellow but you will not be able to give an account of what that thing's being yellow consists in. Even if you can give a scientific account of when/why things appear yellow to people, you will not have succeeded in describing the yellowness of yellow things. The situation with 'good' is the same except that, moreover, good is not even a natural property. Our perception of goodness comes from an intuition: hence Moore is an 'intuitionist'. There are other ways to go about believing in moral truths: for instance that they consist in there being a Form of the Good (Plato), or that they are revealed by God. The important similarity is that in all of these cases, moral truths cannot be accessed via the world of empirical facts. 2) I am an objectivist and I believe that you can derive an 'ought' from an 'is' "I believe that there are such things as ethical truths and that they are logically related to facts, in that you can derive an ethical statement from a factual statement and define ethical terms in terms of non-ethical terms. N.B. the 'ought's that we can derive in this way are categorical 'ought's." An example of a philosopher who holds this kind of view is Searle. In his 1964 'How to Derive an 'Ought' from an 'Is'" he puts forward what he claims is a counterexample to the thesis that you cannot derive an evaluative statement from descriptive statements, using the example of promising. He invokes the idea of institutions to show how a statement like 'someone who has made a promise ought to keep his promise' is tautologous, given that a promise by definition is something that one ought to keep, because the meanings of the terms are derived from the institution that they are part of, here the institution of promising. He states that 'the alleged distinction between descriptive and evaluative utterances is only useful as a distinction between two kinds of illocutionary force, describing and evaluating', and, importantly (interestingly), he
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