It's commonly thought that there is a fundamental divide between fact and value, 'is' and 'ought', such that no amount of knowledge about the former could entail any conclusions involving the latter. But I wonder if the same could be said of facts and apples, 'is' and 'eat'. No matter how many non-apple facts you list, you're not going to end up with a ripe juicy apple. You can't even make any claims about apples. Does it thereby follow that apples are non-natural and fundamentally separate from the rest of reality?
I'm probably missing something. But let's look at the naturalistic fallacy. The 'naturalistic fallacy' is the fallacy of disagreeing with G.E. Moore about whether some property can be given a reductive definition. One proves that an opponent is guilty of this fallacy by professing one's own ignorance; this is known as the 'Open Question argument'. For example, if a chemist proposes that salt can be reduced to sodium chloride, one can expose their fallacy by asking: "I know this shaker contains salt, but does it contain sodium chloride?" The fact that this is an 'open question', as you do not know the answer, demonstrates that salt and sodium chloride cannot be identical after all. For if they were, it would be equivalent to asking "I know this shaker contains salt, but does it contain salt?" and even Cambridge philosophers know the answer to that one!
[Retraction: this post is badly confused. See here and especially here.]