THREE:If the necessity of the One is proved by the inward differentiation of what seemed most simple, it is also proved by the integration of what seems most divided. In his next essay, our philosopher wanders off from the investigation of what he has just begun, by abruptly starting the question whether all souls are one.460 This question is, however, most intimately connected with his main theme. He answers it in the affirmative. Strictly personal as our feelings seem, we are, in reality, one with each other, through our joint participation in the world-soul. Love and sympathy among human beings are solely due to this connexion. Plotinus mentions, as another evidence of its reality, the secret affinities called into play even at a great distance by magical spellsan allusion very characteristic of his age.461 What prevents us from more fully perceiving the unity of all souls is the separateness of the bodies with which they are associated. Matter is the principle of individuation. But even within the soul there is a division between the rational and the irrational part, concentration being the characteristic of the one and dispersion of the other. The latter is fitted by its divided nature for presiding over the bodily functions of sensation and nutrition; and with the dissolution of the body it returns to the unity of the higher soul. There are two ways in which we can account for this pervading unity. It is either as products or as portions of the universal soul that all particular souls are one. Plotinus combines both explanations. The world-soul first gives birth to an image of itself, and then this310 is subdivided into as many partial souls as there are bodies requiring animation.Opposed to the maintenance of standard dimensions are the variations in size due to temperature. This difficulty applies alike to gauging implements and to parts that are to be tested; yet in this, as in nearly every phenomenon connected with matter, we have succeeded in turning it to some useful purpose. Bands of iron, such as the tires of wheels when heated, can be 'shrunk' on, and a compressive force and security attained, which would be impossible by forcing the parts together both at the same temperature. Shrinking has, however, been almost entirely abandoned for such joints as can be accurately fitted.
