We don't know what is real and what isn't.  In fact our whole experience of the world is an illusion created by our brain to enable us to understand an outside world that would bewilder us.  Colors and odors and sounds are created by the brain, to inform us about light waives hitting our eyes and chemicals in the air and sound waves hitting our ears.

People should not completely trust their senses -- no matter how sane we think we are -- they censor what we get, they alter it and often just outright lie to us.