Abstract This chapter discusses whether borderline cases challenge a joint in nature, focusing on a borderline case that putatively has properties that are fundamental to both sides. In particular, the issue is discussed of whether the phenomena of “core cognition” have properties that are fundamental to both perception and cognition. Such cases would be candidates for conceptual perception which would impugn the joint in nature that this book argues for. The chapter starts with a discussion of the perception of causation, arguing that the evidence for perceptual representation of causation is now overwhelming and that “core cognition” of causation can be divided into the perceptual and the cognitive. Similar results apply to numerosity. The conclusion is that “core cognition” is a heterogeneous mixture of perception and cognition.