doi.org/10.1017/S0031819199000248

Hugly, P., & Sayward, C. (1999). Did the Greeks Discover the Irrationals? Philosophy, 74(2), 169–176. doi:10.1017/
So what we are saying is that the demonstration is about geometric figures, whereas the proof that the formula lacks a solution in the rationals if a=b is about numbers, not figures




@johnlard "...we shall argue that geometry forces nothing, that nothing which one sees when one carries out geometrical demonstrations compels one to speak in terms of a number the square of which is two...the Greek geometricians demonstrated was that the area of the square [italics] of the hypotenuse....The letters which enter into the geometric proof stand for the sides [italics] of the triangle, not numbers. They are geometric not arithmetic variables....It is a proof about figures [italics], not numbers....the notion of 'sum' which enters into the proof is not the arithmetical one.... no [italics] rational number measures the hypotenuse in units in terms of which rational numbers measure the sides. It is just a negative [italics] result. That [italics] cannot show us that there nevertheless is [italics] a number which measures the hypotenuse....No number measures anything on its own. Numbers measure only relative to units of measurement....Rather, what we come to see is that there is no unit of length relative to which each [italics] of the sides of a right triangle is measured by rational numbers. ...anyway you choose leaves something unmeasured [italics] by any rational. But nothing forces you to speak in terms of measurement of another sort of number....you can specify its length without bringing in another kind of number - you need only to shift to another unit of measurement...you want [italics] an answer of a certain form. But what shows you that there is [italics] such an answer. The fact that the line has a definite length (it's just as long as it is!) doesn't show that there is a non-approximate answer in terms of inches."
source: "Did the Greeks Discover the Irrationals?"
Professors Philip Hugly, Charles Sayward, University of Nebraska-Lincoln
Philosophy, Vol. 74, No. 288 (Apr., 1999), pp. 169-176 (8 pages)
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