Ideal observer theory

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In metaethics, the ideal observer theory states that ethical judgments should be interpreted as statements about the judgments that a neutral and fully informed observer would make; "x is good" means "an ideal observer would approve of x".

The main idea [of the ideal observer theory] is that ethical terms should be defined after the pattern of the following example: "x is better than y" means "If anyone were, in respect of x and y, fully informed and vividly imaginative, impartial, in a calm frame of mind and otherwise normal, he would prefer x to y."^[1]

While Adam Smith and David Hume are recognized to have espoused early versions of the Ideal Observer theory, Roderick Firth is responsible for starting a more sophisticated modern version. According to Firth, an Ideal Observer has the following specific characteristics: omniscience with respect to nonmoral facts, omnipercipience, disinterestedness, dispassionateness, consistency, and normalcy in all other respects. Notice that, by defining an Ideal Observer as omniscient with respect to nonmoral facts, Firth avoids circular logic that would arise from defining an Ideal Observer as omniscient in both nonmoral and moral facts. A complete knowledge of morality is not born of itself but is an emergent property of Firth's minimal requirements. There are also sensible restrictions to the trait of omniscience with respect to nonmoral facts. For instance, a geological event in another solar system is hardly something necessary to know to make a moral judgment about a case of theft or murder on Earth.

The validity of the Ideal Observer Theory does not rest on the existence of any actual ideal observers actually existing.