be under a delusion

She could see her arm perfectly well but was under a delusion about her body image.

"You are under a delusion, mademoiselle.

It did but increase the difficulty that Judge Pyncheon was under a delusion as to the secret which he supposed Clifford to possess.

One who withdraws oneself from actions, but ponders on their pleasures in the heart, such a one is under a delusion and is a false swimmer of the Way.

It was almost as though he was under a delusion that even the determined arm of the law was not long enough to stretch across the twelve thousand miles separating London from Hobart Town.

Solon was under a delusion when he said that a man when he grows old may learn many things --for he can no more learn much than he can run much; youth is the time for any extraordinary toil.