His system must, then, be received with caution. It is inherently far more probable that the simpler, practical arithmetic would be taught at the elementary schools of letters, which all citizens, including future tradesmen and artisans, attended, not at some later date in a separate school. But can any evidence be found for such an arrangement? Yes, Plato himself in the _Laws_[270] declares that the future builder ought to play with toy bricks and learn weights and measurements when he is a child. His builder, at any rate, cannot wait to learn arithmetic till he is sixteen. Then, in the same work, he quotes the instance of Egypt, where “a very large number of children learn practical arithmetic _simultaneously with their letters_,” and he goes on to commend the methods by which it was taught. Now Egypt in the _Laws_ is represented as the home of ideal education, a sort of Utopia. Again, in Plato[271] Protagoras blames his brother Sophists for “leading their pupils _back_, much against their wish, and casting them _again_ into the sciences from which they have escaped, practical arithmetic and astronomy and geometry and music.” How could the Sophists[272] be described as “leading them back and casting them again” into studies from which they had escaped? Where had they learnt these subjects before they were fourteen? It could only have been at school. But what the Sophists taught must have been new to the boys, or they would not have paid to learn it. It was new, because the Sophists taught the advanced and theoretical stages, which appear in the _Republic_, and the elementary schoolmasters taught the simpler and concrete elements of arithmetic, weights and measures, and the calendar, described in the _Laws_, which were necessary to every Athenian citizen. From all this it may be assumed that the Athenian boys, like Plato’s Egyptian boys, learnt simple arithmetic, weights and measures, and perhaps the calendar, “simultaneously with their letters.”