Tuesday, January 06, 2009

Q67 A2: Whether light is a body?

No. Light cannot be a body because the place of any one body is different from that of any other, nor is it possible, naturally speaking, for any two bodies of whatever nature, to exist simultaneously in the same place; since contiguity requires distinction of place.

Impossibile est lumen esse corpus quod locus cuiuslibet corporis est alius a loco alterius corporis, nec est possibile, secundum naturam, duo corpora esse simul in eodem loco, qualiacumque corpora sint; quia contiguum requirit distinctionem in situ.

Augustine takes light to be a luminous body in act--in other words, to be fire, the noblest of the four elements.

Augustinus accipit lucem pro corpore lucido in actu, scilicet pro igne, quod inter quatuor elementa nobilissimum est.

Aristotle pronounces light to be fire existing in its own proper matter: just as fire in aerial matter is "flame," or in earthly matter is "burning coal." Nor must too much attention be paid to the instances adduced by Aristotle in his works on logic, as he merely mentions them as the more or less probable opinions of various writers.

Aristoteles lumen nominat ignem in propria materia, sicut ignis in materia aerea dicitur flamma, et in materia terrea dicitur carbo. Non tamen est multum curandum de eis exemplis quae Aristoteles inducit in libris logicalibus, quia inducit ea ut probabilia secundum opinionem aliorum.

The powers of movement, intersection, reflection, belong properly to bodies; and all these are attributes of light and its rays. Moreover, different rays of light, as Dionysius says (Div. Nom. ii) are united and separated, which seems impossible unless they are bodies.

Ferri, intersecari, et reflecti est proprie corporum, haec autem omnia attribuuntur lumini vel radio. Coniunguntur etiam diversi radii et separantur, ut Dionysius dicit, II cap. de Div. Nom., quod etiam videtur non nisi corporibus convenire posse.

But all these properties are assigned to light metaphorically, and might in the same way be attributed to heat. For because movement from place to place is naturally first in the order of movement as is proved Phys. viii, text. 55, we use terms belonging to local movement in speaking of alteration and movement of all kinds. For even the word distance is derived from the idea of remoteness of place, to that of all contraries, as is said Metaph. x, text. 13.

Sed omnia illa attribuuntur lumini metaphorice, sicut etiam possent attribui calori. Quia enim motus localis est naturaliter primus motuum, ut probatur in VIII Physic., utimur nominibus pertinentibus ad motum localem, in alteratione et in omnibus motibus, sicut etiam nomen distantiae derivatum est a loco ad omnia contraria, ut dicitur in X Metaphys.