Invitational Theory is rooted in three theoretical foundations, the perceptual tradition, self-concept theory, and a democratic ethos (Purkey, Novak, and Fretz, 2020). This essay focuses in on the first of these foundations, which the author intentionally describes as "perceptual theory." Perceptual theory provides a theoretical foundation for understanding and explaining human behaviour, and could provide very important insights into the offering and receiving of invitations. In this essay the author seeks to re-introduce the Invitational community to this important theoretical foundation, which could profoundly and positively impact the enacting and application of invitational theory. The author begins by providing an overview of perceptual theory, exploring some of the central tenets and implications. The author then reviews the history of the development of the theory, which the author believes has been overlooked and by-passed: not enough people know about perceptual theory. The author introduces a number of perceptual theory basics, which can be a helpful way of introducing the theory. The essay concludes with an exploration of a number of potential implications and applications for the Invitational community.