"Can we say 'both/and'?" is one of my stock questions (see the full stock in the left-hand column).
Generally, the things to be linked with the "and" have something of a competitive or adversarial relationship. They aren't naturally additive, like tea and crumpets; they're the sort of things that might be easier to take one at a time. Hence the question's implied "... rather than 'either/or'?"
The word I usually use to describe this sort of relationship is "tension." You have to be careful with that word, or you might wind up using it to trap the other side of the argument: "Yes, I agree, these two values are in tension. [There, I've conceded the point that you have a point. Now I can freeze your point there, and step around it thusly:] But in these circumstances, it is clear that my value determines the proper course."
It seems to me, though, that you have to be particularly careful with an argument that acknowledges no tension. In general, and assuming good will on everyone's part, everyone in a disputation has a point. Any particular point may happen to be beside the point, but if there is disagreement it has to be coming from somewhere, and it should at least be acknowledged.
I'll even go so far as to suggest that, in certain matters of the Faith, the absence of any tension in an argument may be evidence that the arguer has failed to actually engage the matter.
Mark Shea anticipates this suggestion somewhat, in listing "a number of curious currents of thought that puzzle and intrigue me" about how some people interpret Scripture:
...readers give not the vaguest hint that it disturbs them at all that God should command genocide in the Pentateuch. Hey! He's God! ...
The weird notion that if something in Scripture is mysterious, that's a bad thing....
The correlative notion that anybody who wrestles with these mysteries and comes up with different answers is, not just mistaken, but an "imbecile", an enemy, and a heretic.
The peculiar notion that someplace else, there's a happy land without ambiguity and mystery where diagrams rule and persons can be safely dismissed.
Setting aside a certain baffling hostility toward diagrams, Mark's point is that, since Scripture does not give a closed answer to every question asked of it, closed answers aren't always a good thing.
The Catholic Faith is inherently and inescapably mysterious, and I suggest part of that mystery lies in tension between things -- free will and grace, omnibenevolence and evil, and so forth -- the final key to which Revelation has not provided human reason.
Now, the fact that free will and grace, to choose a much-discussed pair, are in tension doesn't mean that nothing can be said about how they co-exist. It might even be possible to resolve the tension, in the sense of showing how both fit into the entirety of the Faith.
But if the tension is not even recognized, there's a good chance the whole question is being mishandled. And if the tension is completely dissolved -- by, for example, getting rid of free will altogether -- then it's almost certain the answer is wrong.