Galileo Galilei · Science
Galileo’s claim that the universe is written in mathematics - and the bargain that claim struck with the world of colour, taste and feeling.
In The Assayer of 1623, in the middle of a quarrel about comets, Galileo dropped one of the founding sentences of modern science. Nature, he said, is a vast book lying open before us - but we cannot read a word of it until we learn its language, and that language is mathematics. Truth about the physical world is not found by parsing Aristotle or weighing eloquent opinion. It is found by measuring, and by writing what we measure as number, figure and proportion.
Galileo pushes the point to a startling conclusion. Some properties, he argues, genuinely belong to bodies themselves: shape, size, number, position, motion. Strip these away and nothing is left of the object. But other properties - colour, taste, smell, warmth - are different. They are not in the thing; they are produced in us when the thing’s particles strike our senses. Remove the perceiving creature and the redness, the sweetness, the heat simply vanish. Only the geometry remains.
If colour and warmth are not in things, what is? Galileo’s answer is a picture of the world that would dominate science for centuries: matter is nothing but tiny particles - corpuscles - with shape, size, and motion, and everything else is the effect they produce in us. Heat is not a quality smouldering in the fire; it is the agitation of fast-moving particles, which our flesh registers as warmth. A taste is not in the food; it is the action of particles of a certain shape on the tongue. Tickle, he notes, is plainly not in the feather but arises in the body it touches - and colour, taste, and warmth, he argues, are no different. Strip the perceiving animal away and the universe is left as it really is: bodies of definite shape and size, moving and colliding, in silence, without colour, without warmth, without sound.
This is the mechanical philosophy in embryo - the vision of nature as matter in motion, a vast machinery of particles obeying mathematical laws. It is a bleak picture in one way: the rich sensuous world drains out of physical reality and pools entirely in the mind. But it is fantastically productive, because particles with shape, size, and motion are exactly the things mathematics can grip. By reducing the physical world to quantity in motion, Galileo handed it over to geometry - and made possible the mathematical physics that followed.
This is the opening of the lesson. The rest — the dialogue, the primary source, and the recall — is in the app.
You learned that Galileo split the world into measurable qualities and qualities that exist only in the mind. Name which is which, and explain why he built science on the first, in your own words.
Leads to Rene Descartes.
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