If it be true, indeed, that in human practice and the ordinary affairs of everyday life, there is nothing that differs so much from one man as another man (since we each carry in us the weight of hereditary influences, in fluences of race and education accumulated through long periods of time, and the shades of sensibility of each of us are as different as the details of our persons), there is, nevertheless, in that sum total of data which constitute the elements of the moral life of man, a common stock of fundamental truths which form, as it were, a series of moral axioms and a veritable patrimony, proper to all sentient humanity. In all times, and everywhere, indeed, it has always been a fine thing for a man to serve his country, to sacrifice himself for his kind, to honour his parents, to bring up his family well, or, to make use of a formula which contains an epitome of universal morality, to do or not to do to others as we should like others to do or not to do to us, etc. Within a more re strained circle of ideas, we know that in unions of men agglomerated into isolated societies, though they be in dependent or even enemies, there is a common fund of ideas and sentiments. Among soldiers, under whatever nag they serve, the sentiment of military honour is always the same. The esprit de corps, which we see de veloped in certain associations, is nothing but the result ant of a community of ideas and sentiments among all the individuals living in society, and united by the bonds of a vast confraternity.
In all times and places, then, this collection of com mon ideas and sentiments which serves as a basis for phenomena of the moral order, has been, as it were, a sort of directing clue for humanity, a magnetic meridian of common sympathy, by which men have unconsciously regulated their conduct ; and this is so true, this common fund of moral sensibility is so inherent in our natural sensibility, in our very personality ; it is so vivid in us, and so organically constituted, that wherever we find one of our fellow-creatures we judge, a priori, that he must vibrate in the same keys, and thrill to the same impressions. In a word, we believe in the existence of this moral sensibility in others, with the same certainty that we feel regarding the existence of his heart that beats, his lungs that breathe, and his limbs that move according to flexions and extensions previously deter mined.
This common basis of moral sensibility which lives within us and extends to all our fellow-creatures, forming a bond of universal sympathy between all members of the human family, thus becomes the veritable criterion and touchstone that serves us to appreciate and judge of the value of a phenomenon of the moral kind. To a particular phenomenon we logi cally apply a particular method of diagnosis. It is by taking ourselves as a term of comparison, by bringing our conscious personality into the presence of the actions of another, by placing ourselves in imagination in his place, that we arrive at a notion of their scope, and a judgment as to whether they are conformable to the common average-line of human sentiments and universal sensibility.
We thus arrive at the conclusion that there are among mankind fundamental truths of the moral kind, common modes of feeling, which we all uncon sciously obey, and which constitute the common line of average, the common sense, according to which the great human family advances along the path of life. Each of us takes the bearing of his acts more or less from this, and, if these deviate from it, this deviation is then felt by those who are following it, and they accordingly judge of it and condemn it, as a deviation from the common law, and as the patent expression of a perturba tion which has occurred in the faculties of him who has thus got out of the common rut.
We accordingly consider every word, and every piece of writing that is understood and accepted by all, reason able, according to common sense ; while on the other hand, we characterize as unreasonable every action that shocks the notion of right sense and rectitude of judgment, as they exist in others.
Thus, that conception of things in their totality, which we designate under the term reason, is gener ally, from a physiological point of view, nothing but an abstract synthetic expression which serves to express that unconscious tendency we have to follow, in our lives, our ideas, and our actions, the common course followed by our kind, and not to deviate from the meridian line followed by the majority.
Functional Perturbations of of the study of the morbid forms of the operations of the judgment, shows us how closely united one with another are the different phenomena of which it is con stituted, and to what an extent the whole becomes perturbed and disordered, when one of these comes to be disturbed in its mode of action, (especially the first, which is the most important, and the point of departure of the operation which takes place) ; and how far the external expression which results, is in more or less complete discord with the reality of things.
The first phase corresponds, as we have said, to the moment in which the external impression penetrates the sensoriunz, and seizes upon the personality, which immediately participates in the communicated impres• sion. This is the delicate moment of the process, when the terms of the problem are stated. Now, what hap pens when this primordial sensation which should arrive at the sensoriunz with the maximum of precision, and reflect, in as exact a manner as possible, the surrounding phenomena, is incompletely transmitted and falsified ; when, from some accidental disturbance in the different centripetal apparatuses charged with its collection and transmission to the sensoriunz, it arrives there deprived of its essential character and incompletely expressed (sensorial illusions) ? What happens when, on the other hand, the intermediate regions, whose mission it is to transmit to the sensorium peripheral excitations (centres of the optic thalamus), assume a condition of automatic erethism, and proceed, viotu proprio, to launch towards the scnsorium subjective excitations engendered on the spot (hallucinations) ? The human personality, then without any means of direct control, seized upon by fictitious autogenous excita tions, according to natural processes, accepts the change ; receives them, absorbs them, works them up, submits them to the same,subtle operations as though they were the regular and legitimate aliments of its activity ; and henceforward the abnormal process, by means of the working of the energies proper to the cerebral elements, and by virtue of habits formerly acquired, goes on of itself, as logically and inevitably as though it were a pure emanation from the real world ; of course, to the great stupefaction of persons who are not initiated into the knowledge of mental diseases, and cannot bring themselves to admit that a false conclusion may be deduced with perfect logic, and that logic does not imply either the justice or the precision of any judgment what soever.