This paper presents a novel argument against one theoretically attractive form of panpsychism. I argue that “idealist panpsychism” is false since it cannot account for spacetime’s structure. Idealist panpsychists posit that fundamental reality is purely experiential. Moreover, they posit that the consciousness at the fundamental level metaphysically grounds and explains both the facts of physics and the facts of human consciousness. I argue that if idealist panpsychism is true, human consciousness and the consciousness at the fundamental level will have the (...) same metrical structure. However, as I demonstrate, human consciousness does not exhibit the same metrical structure as spacetime. Consequently, the idealist panpsychist faces an explanatory gap between the fundamental consciousness she posits and spacetime. Idealist panpsychism is incompatible with the existence of such an explanatory gap. Thus, idealist panpsychists must close this explanatory gap (which I argue they lack the resources to do), or idealist panpsychism is false. (shrink)