The very first illusion is to believe that there is one, unique world of perception. The mind and the world we experience are inseparable, as it is the mind that makes the world meaningful. Our mind IS our world. Despite the fact that our mental construct of what is perceived is distinct from the objective reality, our mind accepts it as real.
Every organism, man as well as animal, lives in its own subjective spatiotemporal world that semiotic philosophers call ‘Umwelt’ (from the German Umwelt, ‘surrounding world’, or ‘life-world’). According to the biologist Jakob J. von Uexküll, organisms and their life-world shape each other in a functional loop (see fig. below): interactions between the subject and the outer world, mediated through the sense and effect organs, determine the world framework of the subject. Thus, a particular stimulus which has a perceptive cue or meaning to the subject induces always a purposeful reaction.