Everyone can see illusions, including healthy people. Healthy people can sometimes see hallucinations too. Schizophrenics do not necessarily experience hallucinations or even no delusions, for example, with simple schizophrenia. Not everything is so simple and obvious.
the mechanisms of the appearance of hallucinations and illusions are in no way similar to each other. therefore, it cannot be unequivocally asserted that those suffering from schizophrenia can only see hallucinations and cannot see illusions
in the case of illusions, the perception of the world as a system of relations is disturbed. new intra-object relationships appear, namely, illusions. they always SUBSTITUTE some other object. in order for illusions to appear, both the objective conditions of their occurrence (illumination of the room, the design of the object instead of which a person will see an illusion) and subjective conditions (a person's own pre-attunement to see an illusion, an emotional state) must be observed. pathological illusions can be seen by people without any disorders, it is enough only that both conditions for their occurrence are fulfilled. in addition, illusions can be easily dispelled by improving contact with the object.
while hallucinatory images do not replace anything with themselves, they arise not instead of, but ON THE BACKGROUND OF REALITY and require clouding of consciousness. hallucinations, unlike illusions, invade the objective world itself, interact with real objects. they become level with other objects. human behavior in this case fully corresponds to what he perceives.
in schizophrenia, it is hallucinations, not illusions, that are often an integral part of the overall picture of the disease and correspond to the content of delirium. this is facilitated, in addition to the darkened consciousness, also organic diseases of the brain. verbal pseudo-hallucinations usually occur in patients who, for example, having committed a certain negative act, prove that they are not involved in it, that they were forced. thus schizophrenics often hear voices that can intimidate them, threaten, accuse them of something, insult, swear, and so on.
sometimes schizophrenic patients have illusions that are very difficult to distinguish from hallucinosis, but they usually not accompanied by delusions, because there is no degree of clouding of consciousness at which hallucinations occur.