If you interpret this quote more simply, it suggests that people often see us based on their perceptions rather than our true selves. Our actions and identities are shaped by how others view us, and it's difficult to be anything different from their expectations.
Lewis Carroll emphasizes that our true nature and the way we present ourselves are intertwined with others' perceptions. To be authentic, we must recognize that others' views influence our identity, and understanding this can help us navigate how we are perceived in society.