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Aristotle (384-322 BC)
The Physics
translated by R. P. Hardie and R. K. Gaye

Book 1 establishes Aristotle’s scientific method. He recommends beginning with our general understanding of the universe (“the things which are more knowable and obvious to us”) and proceeding from these general ideas to the specific examination (always shaped by our previous understanding) of specific things, or phenomena (“clearer and more knowable by nature”). This is deductive reasoning (starting with a general truth and reasoning your way to logically necessary conclusions) rather than inductive reasoning (beginning with individual observations and reasoning your way towards a general explanation that accounts for them). Modern science relies on inductive reasoning, but not until the sixteenth century would deductive reasoning give way to its rival.

Book 2 defines “nature” in terms of the principle of internal change: Natural things contain within themselves a principle of motion, while things constructed by men (“art”) do not. A sapling grows into a tree because of its intrinsic principle of motion; a house or a bed, although made of wood, never grows into anything else; it is a work of art, and remains a house or a bed. The principle of motion is purposeful: it pushes natural products, inexorably, towards an end which is predetermined, For Aristotle, the cause is from within, always. But he endeavors to explain this purpose without reference either to the Divine Demiurge of Plato, or to the complete random chance suggested by Democritus and the atomists. Purpose in nature is an intrinisic force, detached from any divinity and shaping its own ends.

About this translation

R. P. Hardie and R. K. Gaye were part of a forty-year effort to translate Aristotle into a standard English version. This version, published between 1912 and 1954, is known as the Oxford Translation.

Book I
…The natural way of doing [the science of Nature] is to start from the things which are more knowable and obvious to us and proceed towards those which are clearer and more knowable by nature; for the same things are not “knowable relatively to us” and “knowable” without qualification. So in the present inquiry we must follow this method and advance from what is more obscure by nature, but clearer to us, towards what is more clear and more knowable by nature…Thus we must advance from generalities to particulars; for it is a whole that is best known to sense-perception, and a generality is a kind of whole, comprehending many things within it, like parts.

Book II
Of things that exist, some exist by nature, some from other causes.

“By nature” the animals and their parts exist, and the plants and the simple bodies (earth, fire, air, water)-for we say that these and the like exist “by nature”.

All the things mentioned present a feature in which they differ from things which are not constituted by nature. Each of them has within itself a principle of motion and of stationariness (in respect of place, or of growth and decrease, or by way of alteration). On the other hand, a bed and a coat and anything else of that sort…have no innate impulse to change….

“Nature” then is what has been stated. Things “have a nature” which have a principle of this kind….The term “according to nature” is applied to all these things and also to the attributes which belong to them in virtue of what they are. For instance the property of fire is to be carried upwards–which is not a “nature” nor “has a nature” but is “by nature” or “according to nature”…

A difficulty presents itself: why should not nature work, not for the sake of something, nor because it is better so, but just as the sky rains, not in order to make the corn grow, but of necessity? What is drawn up must cool, and what has been cooled must become water and descend, the result of this being that the corn grows. Similarly if a man’s crop is spoiled on the threshing-floor, the rain did not fall for the sake of this–in order that the crop might be spoiled–but that result just followed. Why then should it not be the same with the parts in nature, e.g., that our teeth should come up of necessity–the front teeth sharp, fitted for tearing, the molars broad and useful for grinding down the food–since they did not arise for this end, but it was merely a coincident result; and so with all other parts in which we suppose that there is purpose?

Wherever then all the parts came about just what they would have been if they had come be for an end, such things survived, being organized spontaneously in a fitting way….

Now mistakes come to pass even in the operations of art: the grammarian makes a mistake in writing and the doctor pours out the wrong dose. Hence clearly mistakes are possible in the operations of nature also. If then in art there are cases in which what is rightly produced serves a purpose, and if where mistakes occur there was a purpose in what was attempted, only it was not attained, so must it be also in natural products, and monstrosities will be failures in the purposive effort.

….It is absurd to suppose that purpose is not present because we do not observe the agent deliberating. Art does not deliberate. If the ship-building art were in the wood, it would produce the same results by nature. If, therefore, purpose is present in art, it is present also in nature.

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