This mental state drives him to madness. Alternation of his moods and understanding. One moment he sees a thing and another moment he does not understand it. One moment she sees it is her child and another that it is not. One moment thinks it is so and next moment has enough reason left that it is not so .
Delusion is an advanced stage of illusion.
In the Repertory we have the same remedies often in illusion and delusion, it is a matter of grade. When the intellect is slightly affected it is an illusion, and what he sees he knows is not so. He sees demons, and at first he knows from his intelligence that a demon is not there, but later, he wants you to drive him out. It does not matter which, they are similar symptoms, and it is a matter of degree, and so, in the Repertory, delusions and illusions are not given separate places. Anac., Hyos., Stram, and Bell .