 A third question is what gives representations their semantic content. There are three families of views. Instrumentalists believe that ascribing semantic content to things is just heuristically useful for prediction and explanation; semantic properties are not real properties of computational states (e.g., Dennett 1987, Egan 2010). Realists who are not naturalists believe semantic properties are real properties of computational states, but they are irreducible to non-semantic properties. Finally, realists who are also naturalists believe semantic properties are both real and reducible to non-semantic properties, though they disagree on exactly how to reduce them (e.g., Fodor 2008, Harman 1987).