Greek εἰκασία, "guess, suppose, conjecture." The lowest of the four states of consciousness. As you can see from the meaning of the word, eikasia is not based on facts, but is a projection of the mind, an illusion.
This term is used by Plato to signify imagination that is focused exclusively on a temporal appearance or image; in other words, fantasy or illusion, one of the sources of suffering. This state of consciousness corresponds to the most unconscious and mechanical levels of the psyche, and relates also to the state of physical sleep (within which the consciousness is wandering within the subjective, inferior levels of the psyche, also called "dreaming").
"Eikasia is ignorance, human cruelty, barbarism, exceedingly profound sleep, a brutal and instinctive world, an infra-human state." - Samael Aun Weor, The Perfect Matrimony