The denial of the substantial unity of the person could claim from very different positions. It should be recalled, for example, the philosophies of Plato and Philo who admitted the existence of several souls, or psychological phenomenalism in which there is no substance that is identity support any facts or psychological associations. According to this view, in the person there would be nothing truly permanent but the person would rather a construction project ever is finally dissolved into your own personal activity. But without doubt the dualisms trends that have broken a sharper shape with the unity of the human person.
For Plato and Descartes, for example, the union of soul and body is merely accidental. For the latter, the soul is only as "prisoner" of his own body, but a "res cogitans" that moves the body to which it is joined by the pineal gland. Not the first time that metaphors that are like the captain of our ship suggest this lack of integral unit. By contrast the Aristotelian tradition was more faithful to the defense of the substantial unity of man, which would form a complete unit consisting of two substantial coprincipios: body and soul. So the living being would have two dimensions: an organic matter and a vital principle that organizes and enlivens this matter.
The soul would not be an existing intangible element that binds to an existing but lifeless body as the body without the soul would not be an organized and living body. Yet, as we shall see, the real improvement of anthropological dualism will be linked to the ability to recognize a third element in the union and identity that has every human person. This third element will not be a feature of human nature, but being. Indeed, the existence or act of being is the element that definitely confers unity to the whole human compound unit over time and ontological dignity prior to any further action, as any action will the course existential foundation of his performance. The living being is characterized in that it moves itself. The automotive becomes a sign of unity of being alive, as is the case with self-realization.
Indeed we see that living beings have a remarkable degree of internal unity. It is true that this unit can occur in varying degrees or levels, since it is not the same degree of immanence which occurs in only vegetative life, and we discovered in acts of nutrition, growth or generation, which discovered on sensitive life where often the circuit diagram or between the stimulus and response breaks. It is very clear that an animal may choose or decide the best means to meet their basic needs, moving from one place or another, preferring to escape danger or hide from it. The higher the level of greater unity will be the symptoms of autonomy in which life is exercised. (...)