  But Metaphysical Naturalism is not an unproblematic thesis. What does the naturalness of a fact or property consist in, exactly? That’s a pretty basic question, but philosophers are often left embarrassingly tongue-tied when called on to answer it. Some claim (e.g., Bedke 2009, Enoch 2010, Lutz forthcoming) that natural properties or facts are those that have causal or explanatory power, while others have attempted to distinguish natural properties from non-natural properties in other metaphysical terms (see McPherson 2015). But the difficulty of defining a “natural” property, often combined with a general Humean or Kantian skepticism about philosophers’ ability to meaningfully investigate any metaphysical questions, has made many philosophers wary of discussing Metaphysical Naturalism directly. Accordingly, many define moral naturalism through the lens of Analytic Naturalism or Epistemic Naturalism.