 The thesis about post-perceptual conception of a SQ entails two claims that are directly relevant: that we cannot form the concept of a SQ without at the same time forming the concept of the sensation it causes and that we cannot have the concept of a SQ unless we have experienced the quality. The need for experience is often taken to support the view that PQs and SQs differ in respect of how their meanings are specified: in particular, it is said that “X is red” means that X manifests sensations of red under certain circumstances, whereas the meaning of “X is solid” can be specified without reference to sensations of solidity. But recent scholars argue that the semantic claim about SQ terms is not entailed by the capitol part remark. They point to reasons for a person’s needing to have the concept of the sensation caused by a quality in order to have the concept of that quality—the capitol part thesis—that are independent of the truth or falsity of the semantic claim. Van Cleve points to the use Kripke might make of the perception of SQs to fix the reference of “red” in its rigid use, i.e., use as a name for just those qualities that cause a certain sort of sensation in the actual world. Nichols (2006: 6.4) offers a different reason for a similar conclusion. But although recent scholars agree about this, they disagree over how Reid intended the capitol part thesis to be understood.