TITLE: Can $\Delta^{1}_{2}$ separate degrees of constructibility?
QUESTION [7 upvotes]: Suppose that $\phi(x)$ is a $\Delta^{1}_{2}$-formula (without parameters) and let $A:=\{x\subseteq\omega:\phi(x)\}$. It is clear that, e.g. if there are Cohen-generics over $L$, then $A$ cannot be the set of constructible reals, roughly because $\Delta^{1}_{2}$ cannot distinguish between sufficiently high Cohen-generics in $L$ and Cohen-generics over $L$. I wonder whether this can be strengthenend in the following way:
Given appropriate largeness assumptions (existence of generic filters, large cardinals...), at least one of $A$ and $\mathfrak{P}(\omega)\setminus A$ contains real numbers of all degrees of constructibility. In other words, can $\Delta^{1}_{2}$ "separate" degrees of constructibility in a nontrivial way?

REPLY [5 votes]: Expanding on Douglas Ulrich's answer:
Note that this question is only meaningful when there are nonconstructible reals since otherwise there is only one constructibility degree. 
If there is a nonconstructible real and $A$ is $\Delta_2^1$ set, then either $A$ or $\mathbb{R} \setminus A$ is a $\Sigma_2^1$ set of reals with a nonconstructible element. Without loss of generality, suppose $A$ has the nonconstructible real. By the Mansfield-Solovay theorem (using the $\omega_1$-Suslin representation via the Shoenfield Tree $S$ for $A$ which belongs to $L$), there is a constructible tree $T$ so that $[T] \subseteq A$. 
Every constructible tree is an $L$-pointed tree. So $[T]$ has every $L$-degree.