Thales seems to have spent the early part of his life as a merchant, becom
ing wealthy enough to devote the latter part of his life to study and some travel.
It is said that he resided for a time in Egypt, and there evoked admiration by
calculating the height of a pyramid by means of shadows (see Problem Study
3.1). Back in Miletus, his many-sided genius won him a reputation as a states
man, counselor, engineer, businessman. philosopher, mathematician, and as
tronomer. Thales is the first know indivedual
with whom mathematical discov
eries are associated. In geometry, he is credited with the
1. A circle is bisected by any diameter.
2. The base angles of and isosceles triangle
3. The vertical angles formed by two
intersecting lines are equal.
4. Two triangles are congruent if they have
two angles and one side in
equal. [Thales perhaps used this result in his
determination of the distance of a ship
form shore (see Problem Studdy 3.1).]
5. An angle inscribed in a semicircle is a (This was recognized by the Babylonians
right some 1400 years earlier.)
The value of these results is not to be measured by the theorems themselves. but rather by the belidf that Thales supported them by some logical reasoning
instead of intuition and experiment.
As with other great men, many charming anecdoted are told about Thales
that, if not true, are at least apposite. There was the occasion when he demon
strated how easy it is to get rich:foreseeing a heavy crop of olives coming, he
obtated a monopoly on all the oil presses of the region and then later realized a
fortune bu renting them out. And there is the story, recounted by Aesop, of the
readlditrant mule that, when transporting salt, found that by rolling aver in the
stream he could dissolve the contents of his load and thus travel more lightly
Thales broke him of the troublesome habit by loading him with sponges. He
answered Solon's query as to why he nevermarried by having a runner appear
next day with a fictitious message for Solon stating that Solon's favorite son
had been suddenly killed in an accident. Thales then calmed the grief-stricken
father, explanined everything, and said, "I merely wanted to tell you why I
Recent research indicates that there is no evidence backing an aften- re
peated story that Thales predicted a solar eclipse that took place in 585 B.C.