One challenge to relationism in general relativity is that the metric field is underdetermined by the stress-energy tensor. This is manifested in the existence of distinct vacuum solutions to Einstein’s equations. In this paper, I reformulate the problem of underdetermination as a problem from vacuum solutions. I call this the vacuum challenge and identify the gravitational degrees of freedom (associated with the Weyl tensor) as the “source” of the challenge. The Weyl tensor allows for gravitational effects that something outside of a system exerts on the system. I provide a relationist response to the vacuum challenge.