By (I) a sensory hallucination or (2) a massive sensation, both being of telepathic origin.
The contents of experience are not all alike true or valid: hallucination is possible; here the Stoics join issue with Epicurus.
Prof. Josiah Royce has suggested for this supposed form of hallucination the term "pseudo-presentiment."
She'd dared to hope again that everything was a hallucination brought on by too much alcohol, until Toby burst in chasing a cat she didn't remember owning.
Among proposed normal explanations of these phenomena that of hallucination (q.v.), including illusion as to what is seen almost amounting to hallucination, deserves careful consideration.
What then happened was very natural: imitations of the old wares were produced, and having been sufficiently disfigured by staining and other processes calculated to lend an air of rust and age, they were sold to ignorant persons, who labored under the singular yet common hallucination that the points to be looked for in specimens from early kilns were, not technical excellence, decorative tastefulness and richness of color, but dinginess, imperfections and dirt; persons who imagined, in short, that defects which they would condemn at once in new porcelains ought to be regarded as merits in old.
His moral character was undoubtedly weak in other ways than this, but it is fair to remember that but for his astounding Confessions the more disgusting parts of it would not have been known, and that these Confessions were written, if not under hallucination, at any rate in circumstances entitling the self-condemned criminal to the benefit of considerable doubt.
From an evidential point of view the apparition is the most valuable class of death-warning, inasmuch as recognition is more difficult in the case of an auditory hallucination, even where it takes the form of spoken words; moreover, auditory hallucinations coinciding with deaths may be mere knocks, ringing of bells, &c.; tactile hallucinations are still more difficult of recognition; and the hallucinations of smell which are sometimes found as death-warnings rarely have anything to associate them specially with the dead person.
If we take it strictly to mean the belief in ghosts or spirits having the " vaporous materiality " proper to the objects of dream or hallucination, it is certain that the agency of such phantasms is not the sole cause to which all mystic happenings are referred (though ghosts and spirits are everywhere believed in, and appear to be endowed with greater predominance as religious synthesis advances amongst primitive peoples).
The persistent belief on the part of the narrators in the genuineness of their previsions indicates that in some cases there may be a hallucination of memory, analogous to the well known feeling of "false recognition."