  The last suggestion turns on a step in reasoning that moves from facts that can be specified non-morally and are taken on all sides to be open to empirical study to moral facts. This step has been claimed by numerous philosophers to be a fallacious step in deductive reasoning. Some of these philosophers hold that the moral claims are not true or false and hence cannot express moral knowledge (Ayer 1946, Stevenson 1944 and 1963, Hare 1952 and 1981, Gibbard 1990, Blackburn 1984 and1998). Others, such as Kant and G. E. Moore, hold that moral knowledge is possible but not deducible from experience of the natural world. Moore’s argument, however, is worth considering in its own right, since it has had significant influence since he first articulated it in 1903 and differs from Kant’s. For Moore, what would have to be the case to allow the reasoning to go through would be the identity of a moral property with a property specifiable in terms describing the natural world. For example, if the property of being morally good is the same as the property of being pleasurable, then from the empirically ascertainable fact that an activity is pleasurable one can deduce that the activity is morally good. Moore thought, however, that no naturalistically specifiable property, such as being pleasurable, could possibly be the same as a moral property. In fact, his position was more general. He called it a “naturalistic fallacy” to suppose that a moral property is the same as some natural property, however the latter property might be specified. In his language, moral naturalism, in either to the two forms considered, would be an example of the naturalistic fallacy. 