  The origin of analytic philosophy can be associated with G.E. Moore. His Principia Ethica (1903) can be regarded as the first major ethical document of the school. He was strongly influenced by Sidgwick at Cambridge, but rejected Sidgwick's negative views about intuitionism. He thought that intrinsic goodness was a real property of things, even though (like the number two) it does not exist in time and is not the object of sense experience. He explicitly aligned himself here with Plato and against the class of empiricist philosophers, ‘to which most Englishmen have belonged’ (Principia Ethica, 162). His predecessors, Moore thought, had almost all committed the error, which he called ‘the naturalistic fallacy,’ of trying to define this value property by identifying it with a non-evaluative property. For example, they proposed that goodness is pleasure, or what produces pleasure. But whatever non-evaluative property we try to say goodness is identical to, we will find that it remains an open question whether that property is in fact good. For example, it makes sense to ask whether pleasure or the production of pleasure is good. This is true also if we propose a supernatural property to identify with goodness, for example the property of being commanded by God. It still makes sense to ask whether what God commands is good. This question cannot be the same as the question ‘Is what God commands what God commands?’ which is not still an open question. Moore thought that if these questions are different, then the two properties, goodness and being commanded by God, cannot be the same, and to say (by way of a definition) that they are the same is to commit the fallacy. Intrinsic goodness, Moore said, is a simple non-natural property (i.e., neither natural nor supernatural) and indefinable. He thought we had a special form of cognition that he called ‘intuition,’ which gives us access to such properties. By this he meant that the access was not based on inference or argument, but was self-evident (though we could still get it wrong, just as we can with sense-perception). He thought the way to determine what things had positive value intrinsically was to consider what things were such that, if they existed by themselves in isolation, we would yet judge their existence to be good.