Why is Charlie saying no one I have ever known is what he appears to be on the surface in flowers of algernon?

In "Flowers for Algernon," Charlie states that no one he has ever known is what they seem on the surface to highlight the theme of hidden complexities in human nature. His experience, particularly as he undergoes an intelligence-enhancing procedure, reveals that people often conceal their true feelings, insecurities, and motivations behind facades. This realization reflects Charlie's growing understanding of the depth of human relationships and the challenges of perception, reinforcing the idea that appearances can be deceiving.