Details and arguments are given to better show how sensation and perception relate to conventional reality (reality as it appears through psychological functioning) and objective reality (reality that exists independently of psychological functioning). Limitations of human perception and how the brain works as a “heuristic” machine is demonstrated through a variety of examples. The binding problem is also discussed, which has implications for why conventional reality is so difficult to “unsee” (i.e., why ultimate reality is difficult to realize). Overall, this chapter focuses on showing that sensation, perception, and conventional reality is a small, subjective sliver of objective reality and has no permanent basis, which has critical ramifications for mental health.