Fact and Value
It seems to be commonly assumed that fact and value belong to separate categories: facts are not values and values are not facts. We might call this Humean dualism. The two categories are held to be exclusive and exhaustive. But is the dualism really so clear-cut? First, there is the question of how homogeneous each of the alleged categories is (the same question applies to Cartesian dualism): aren’t there many types of fact and many types of value? Maybe a more pluralist view would be better.  But second, aren’t facts valuable and values factual? Facts can be good, bad, or indifferent—they are not value-neutral. Pleasure is good, pain is bad, and hedonic neutrality is a matter of indifference. Every fact can in principle bear on our desires, wishes, emotions, and judgments of desirability—not to mention our aesthetic values. The fact that there is oxygen in the earth’s atmosphere, for example, has value so far as terrestrial animals are concerned. Also, values are themselves matters of fact: it is a fact that pleasure is good, say, and genocide is bad. Don’t say that such judgments are subjective or relative or mere projections: that doesn’t render them non-factual, since there are subjective, relative, or projected facts (take colors). Facts don’t need to be objective in order to be facts (not that we should accept these subjectivist views of value). Even tastes and emotions are factual (it’s a fact that blue cheese tastes good to me).  The truth is that statements about value, like other statements, are statements of fact—they are true or false, believable or not believable. What we really have is a dichotomy between non-value statements of fact and value statements of fact. So all (non-value) facts have a value aspect and all values are species of fact. The world isn’t divided into a set of value-free facts and a parallel set of non-factual values: value facts are among the facts of the world, and the non-value facts are value-imbued. It is true that reality contains two sorts of property—value properties and non-value properties—and we have vocabulary suited to both sorts of property; but this implies no grand metaphysical division between fact and value. Facts are not intrinsically opposed to values, and values are not prohibited from belonging to the fact club. It would be better to say that everything in the world is a combination of value properties and non-value properties (compare certain views of the mental and the physical). The case is analogous to primary and secondary qualities: there are indeed two types of property, but it would be wrong to express this by saying that primary qualities correspond to facts while secondary qualities don’t, or that primary qualities can exist without accompanying secondary qualities. Primary qualities come with associated secondary qualities, and both are perfectly factual (even if secondary qualities are subjective or relative or some such). The shape-color distinction is not a distinction between the factual and the non-factual. Likewise goodness is a property belonging to facts in the sense that ascriptions of goodness are factual, and insofar as non-moral facts have a moral aspect (or other evaluative aspect). The world is a combination of value properties and non-value properties, as it is a combination of primary and secondary properties. There are not two worlds, one of fact and the other of value. These distinctions should not be inflated beyond their proper dimensions. 
 Values fall into several subspecies: moral, aesthetic, practical, taste, whim, caprice, existential, etc. It would be wrong to assume that all these values form a homogeneous group; in particular, moral values are really nothing like food preferences or an appetite for fast living. It is the same for the mental side of traditional mind-body dualism: what we call “the mind” includes sensations, beliefs, moods, wishes, linguistic understanding, character traits, etc. We shouldn’t let a high-level dualism blind us to deep differences within a broad category.
 I am not considering such doctrines as emotivism and prescriptivism, which assume a highly tendentious conception of the factual and have little basis in the actual semantics of moral sentences. Moral sentences have the grammar of truth-bearing propositions (you can easily slide them into a Tarski-style biconditional).