Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/48

 Page 23 a case can never happen: and though it should, and that the separated part should return to its whole, it would not return as grave or light, for that the same Aristotle proveth, that the Cœlestial Bodies are neither heavie nor light.

With what reason I doubt, whether grave bodies move by a right and perpendicular line, you shall hear, as I said before, when I shall examine this particular argument. Touching the second point, I wonder that you should need to discover the Paralogism of Aristotle, being of it self so manifest; and that you perceive not, that Aristotle supposeth that which is in question: therefore take notice.

Pray Salviatus speak with more respect of Aristotle: for who can you ever perswade, that he who was the first, only, and admirable explainer of the Syllogistick forms of demonstration, of Elenchs, of the manner of discovering Sophisms, Paralogisms, and in short, of all the parts of Logick, should afterwards so notoriously equivocate in imposing that for known, which is in question? It would be better, my Masters, first perfectly to understand him, and then to try, if you have a minde, to oppose him.

Simplicius, we are here familiarly discoursing among our selves, to investigate some truth; I shall not be displeased that you discover my errors; and if I do not follow the mind of Aristotle, freely reprehend me, and I shall take it in good part. Onely give me leave to expound my doubts, and to reply something to your last words, telling you, that Logick, as it is well understood, is the Organe with which we philosophate; but as it may be possible, that an Artist may be excellent in making Organs, but unlearned in playing on them, thus he might be a great Logician, but unexpert in making use of Logick; like as we have many that theorically understand the whole Art of Poetry, and yet are unfortunate in composing but meer four Verses; others enjoy all the precepts of Vinci*, and yet know not how to paint a Stoole. The playing on the Organs is not taught by them who know how to make Organs, but by him that knows how to play on them: Poetry is learnt by continual reading of Poets: Limning is learnt by continual painting and designing: Demonstration from the reading of Books full of demonstrations, which are the Mathematical onely, and not the Logical. Now returning to our purpose, I say, that that which Aristotle seeth of the motion of light bodies, is the departing of the Fire from any part of the Superficies of the Terrestrial Globe, and directly retreating from it, mounting upwards; and this indeed is to move towards a circumference greater than that of the Earth; yea, the same Aristotle makes it to move to the concave of the Moon, but that this circumference is that of the World, or concentrick to it, so