To be frank: no.
https://www.reddit.com/r/Catholicism/comments/3ghjwh/nondisc...>There are a number of readily plausible accounts of metaethical naturalism that are available to the atheist. See, for example, Firth 1952, Railton 1986, Boyd 1988, Brink 1989, Smith 1994, or Foot 2001. My point is not that any of these accounts are correct (although I think that some of them are fairly likely to be true). Rather, my point is that if they are false, they are not obviously false. This means that they present the atheist with plausible accounts of objective morality that feature only natural facts, overturning claim (c) and, therefore, claim (a) as well.
>Claim (d) fails on two fronts. First, there are non-natural facts that can serve as truth makers for moral claims that are available to atheists and, second, any problem that the atheist faces with regards to these facts the theist faces just as badly. I take the first horn to be supported by the possibility of irreducibly normative properties, Platonic or otherwise, that are available to the atheist. Recent defenses of such views include Shafer-Landau 2003, Cuneo 2007, Wedgwood 2007, Enoch 2011, and Cuneo & Shafer-Landau 2014.
>On the latter point, that the theist faces the same problems as the atheist when it comes to non-natural normative facts (if there are any such problems), I agree with Heathwood 2012 that there cannot be any coherent theistic moral constructivism which does not refer to some irreducibly normative properties. Properties that are equally available to the atheist.