"Aristotle observes that the One is reasonably regarded as not being itself a number, because a measure is not the things measured, but the measure or the One is the beginning (or principle) of number. This doctrine may be of Pythagorean origin; has it; Euclid implies it when he says that a unit is that by virtue of which each of existing things is called one, while a number is 'the multitude made up of units'; and the statement was generally accepted. According to Iamblichus, (an ancient Pythagorean, probably not later than Plato's time) defined a unit as 'limiting quantity'... or, as we might say, 'limit of fewness', while some Pythagoreans called it 'the confine between number and parts', i.e. that which separates multiples and submultiples. Chrysippus (third century B.C.) called it 'multitude one',... a definition objected to by Iamblichus as a contradiction in terms, but important as an attempt to bring 1 into the conception of number."