Final answer:
Delusions are persistent false beliefs, hallucinations are perceptions without external stimuli, and illusions are distorted perceptions of real stimuli. Delusions concern belief; hallucinations lack real stimuli; illusions misrepresent actual sensory input.
Step-by-step explanation:
Delusions, hallucinations, and illusions represent different types of perceptual disturbances that can significantly impact an individual's grasp on reality. A delusion is a firmly held, false belief that persists despite evidence to the contrary and is not typically influenced by cultural or religious beliefs. It can manifest as paranoia or grandeur, such as believing one is an entity sent from God when there is no basis for this belief. Hallucinations are perceptual experiences that occur without an external stimulus; for example, hearing or seeing something that isn't there, like the devil appearing as God.
These experiences can be visual, auditory, tactile, olfactory, or gustatory and can occur under the influence of hallucinogens or due to psychiatric conditions. An illusion is a misperception or distorted perception of a real external stimulus. An example would be an optical illusion where lines of equal length appear different due to their contextual presentation. While all three phenomena involve a departure from objective reality, delusions relate to belief, hallucinations to perception without real stimuli, and illusions to misleading perceptions of real stimuli.