[3] In regard to the matter testified, that is, in regard to the object of the testimony; it is, first of all, a requisite condition, that what is reported to be true should be possible, both absolutely, or as an object of the elaborative Faculty, and relatively, or as an object of the Presentative Faculties,--Perception, External or Internal. A thing is possible absolutely, or in itself, when it can be construed to thought, that is, when it is not inconsistent with the logical laws of thinking; a thing is relatively possible as an object of perception, External or Internal, when it can affect Sense or Self-consciousness, and, through such affection, determine its apprehension by one or other of these faculties. A testimony is, therefore, to be unconditionally rejected, if the fact which it reports be either in itself impossible, or impossible as an object of the representative faculties. But the impossibility of a thing, as an object of these faculties, must be decided either upon physical, or upon metaphysical, principles. A thing is physically impossible as an object of sense, when the existence itself, or its perception by us, is, by the laws of the material world impossible.--Hamilton's Logic 460.--Ed. [4] "_Light_,--great _Light_."--It will be noticed that this "light" is presented first objectively as a phenomenon, a thing, But what is "light"? The universal answer is "That force in nature which, acting on the Retina of the eye produces the sensation we call vision." This vision is the total of the subjective effect of that agency of Nature, the subjective realization through the functions of the Cerebellum. But functions are accomplished through agencies called organs. The retina is one of these organs. Through the operations of these organs and cerebellum subjective apprehension is produced as an effect, but in some cases of very forcible apprehensions they are interpreted as a diseased condition of the organs of sense. Ideas sometimes acquire unusual vividness and permanence and are, therefore, peculiarly liable to be mistaken for their objective prototypes and hence specters, spectral allusions which are very common in cases of emotional excitement.