Plotino - Tratado 44,24 (VI, 3, 24) — As espécies de movimento: movimento local

24 Pasando al movimiento local, si moverse hacia arriba es contrario a moverse hacia abajo y moverse circularmente es distinto de moverse rectilíneamente, ¿en qué está la diferencia? ¿Qué diferencia hay, por ejemplo, entre arrojar una piedra por encima de la cabeza y arrojarla a los pies? Porque la fuerza impulsora es la misma. A no ser que uno diga que uno es el impulso hacia arriba y otro y de otro modo, comparado con el movimiento hacia arriba, el impulso hacia abajo, sobre todo si el movimiento es natural, supuesto que la fuerza impulsora es, en un caso, la ligereza, y en el otro, la pesadez. Pero común e idéntico en ambos es el moverse al lugar propio. Así que me temo que en este caso la diferencia proviene de factores extrínsecos. En el caso de los movimientos circular y rectilíneo, si lo mismo que el recorrido es rectilíneo podría ser circular, ¿en qué está la diferencia si no es en la figura del trayecto? A no ser que uno diga que el circular es una mezcla por no ser movimiento plenamente ni desplazamiento completo. Pero parece que el movimiento local es un mismo movimiento que se diferencia con diferencias extrínsecas.

XXIV. Quand il s’agit du mouvement de déplacement, on peut se demander si monter est le contraire de descendre, en quoi le mouvement circulaire diffère du mouvement rectiligne, quelle différence il y a entre jeter un objet à la tête ou le jeter aux pieds. On ne le voit pas clairement : car dans ces cas la puissance locomotrice est unique. — Dira-t-on qu’il y a une puissance qui élève et une autre qui abaisse, que monter est une manière d’être différente de descendre, surtout si ces mouvements sont naturels, s’ils ont pour cause la légèreté et la pesanteur? Dans ces deux cas, il y a quelque chose de commun, c’est de se porter vers son lieu naturel, en sorte que la différence provient alors des choses extérieures. En effet, dans le mouvement circulaire et le rectiligne, si quelqu’un meut le même objet tour à tour circulairement et en ligne droite, quelle différence y a-t-il dans la puissance motrice? On ne saurait tirer la différence que de la figure même du mouvement, à moins qu’on ne dise que le mouvement circulaire est composé, qu’il n’est pas un véritable mouvement et qu’il ne produit par lui-même aucun changement. Dans tous les cas, le mouvement de déplacement est un et n’a que des différences extrinsèques.

MOVEMENT OF DISPLACEMENT IS SINGLE.

24. As to movement of displacement, we may ask if ascending be the opposite of descending, in what the circular movement differs from the rectilinear movement, what difference obtains in throwing an object at the head or at the feet. The difference is not very clear, for in these cases the motive power is the same. Shall we say that there is one power which causes raising, and another that lowers, especially if these movements be natural, and if they be the result of lightness or heaviness? In both cases, there is something in common, namely, direction towards its natural place, so that the difference is derived from exterior circumstances. Indeed, in circular and rectilinear movement, if someone move the same object in turn circularly and in a straight line, what difference is there in the motive power? The difference could be derived only from the figure (or outward appearance) of the movement, unless it should be said that the circular movement is composite, that it is not a veritable movement, and that it does not produce any change by itself. In all of these cases, the movement of displacement is identical, and presents only adventitious differences.

24. With regard to locomotion: if ascending is to be held contrary to descending, and circular motion different [in kind] from motion in a straight line, we may ask how this difference is to be defined - the difference, for example, between throwing over the head and under the feet.

The driving power is one - though indeed it might be maintained that the upward drive is different from the downward, and the downward passage of a different character from the upward, especially if it be a natural motion, in which case the up-motion constitutes lightness, the down-motion heaviness.

But in all these motions alike there is the common tendency to seek an appointed place, and in this tendency we seem to have the differentia which separates locomotion from the other species.

As for motion in a circle and motion in a straight line, if the former is in practice indistinguishable from the latter, how can we regard them as different? The only difference lies in the shape of the course, unless the view be taken that circular motion is "impure," as not being entirely a motion, not involving a complete surrender of identity.

However, it appears in general that locomotion is a definite unity, taking its differences from externals.