The division of ideas into spiritual and sensual is important in our theory, because we believe the second alone form the material for hallucinations, and that, if the first appear to participate in them, it is only by the abuse of abstraction, or an imperfection in our nature, which gives material forms to spiritual things. Independence of mind is manifested beneath the false sensations. Sensation reaches the brain imperceptibly, but attention causes it to reappear, visible in proportion to its strength, so that, although at first confused, by degrees clearer, it ends by developing itself palpably to the sight. The repetition of this may lead the most sensible men into error. According to Crichton, the continuance of the operations of the mind in hallucinations and monomania proves that all portions of the brain are not the seat of this phenomenon.

A powerful emotion, or a violent passion, so color, animate, and vivify ideas, that they may take a material form.

Concentration of attention plays an important part in the theory of the hallucinations of celebrated persons. The facts, on which it rests, are those where hallucinations is reproduced by an effort of the will. This theory is not always admissible, and it is with reason that hallucinations have been referred, in the intermediate state of sleeping and waking, to enfeebled attention. In this case occurs what has been observed in several pathological states, where two opposite conditions occasion symptoms apparently similar.

Nothing is more usual with nervous and impressible subjects, unenlightened by education, than to see preoccupation of mind become extreme at the approach of night, and during darkness, and give birth to the most strange and alarming creations.

Imagination exercises its influence in hallucinations; it is also remarked that they are often a painted reflex, the pictures of the thoughts and of the habitual occupations of the individual.

Memory is not less active in the formation of hallucinations, for they are often reminiscences, recollections of long past sensations placed in the brain, recalled by the well-known law of association, and to which a physical or moral cause gives all the vivacity of actual sensation.

Erroneous beliefs, which may be called the hallucinations of reason, should be studied in their formation, because they exert a great influence on the production of social and individual hallucinations.

False ideas play a considerable part in the production of hallucinations. They are no less important in the creation of insanity. This argument appears to decide the predominance of moral over physical causes.

Their origin must be referred to forgetfulness of the two great laws of mankind, the knowledge of God and of self; whence arises the desire for the unknown, the wish to believe, the love of the marvellous, the thirst of emotion, and the ardor for knowledge; all so many sources of hallucinations.

In many cases, hallucination is nothing extraordinary; it is almost a normal state consistent with reason, and it is easy to perceive, how so many celebrated men have exhibited this symptom, without being insane.

When the actions of an illustrious man are under review, we must never lose sight of the period in which he lived. The world of Cosmao was very different from that of Galileo, and yet reason was the same in both epochs.

In all philosophical study of man, his duality must be recognized; without this consideration, it will be impossible to understand either his history or his biography; that is to say, either his spiritual or his mortal existence.

The hallucinations of many celebrated men belong to their age and not to the individual; a proof of which is, that their actions are distinguished by the highest wisdom; their enterprises exhibit superior faculties, admirable judgment, great expansion of mind, and love of their fellow-creatures.

The hallucinations of these personages cannot be compared with those of madmen; they were the representatives of an epoch, a need, an idea; they must of necessity have done as they did; their mission was a providence.

Real hallucinations are never without a mixture of insanity. The examples of hallucinated persons, who have, with a false idea, fulfilled important functions, are very rare, and have reference to individuals, who, being conscious of their state, kept a strict watch over themselves.

No one of these hallucinated persons has been situated in a like manner to those of whom we speak. No one has been the expression of a useful thought. No parallel can be established between the powerful, creative, and animated organizations of the former; and the weak, plagiaristic, and sickly nature of the second. Individuals of both these sections have had hallucinations; but in the one case they were the result of the times, and exercised no influence on reason; whilst in the other, they have ever been more or less complicated with insanity.

Every historical epoch, having its own peculiar characteristics in actions, and in thoughts, is summed up in one man, who is the natural expression of it.

A well-defined line of demarcation ought to be established between the apparitions of Scripture and the hallucinations of profane history, and even of many Christians. The former, we are convinced, are only explainable by divine interposition, whilst many of the second are referable to the belief of the times, certain psychological conditions, and to the morbid state of the brain.