History of the Greek alphabet retained the sound. A symbol based on the left-hand half ( ├ ) of the letter Η was therefore sometimes used to indicate the presence of where necessary, and its absence was indicated by a symbol based on the right half. During the classical period, ΕΙ came to be pronounced and ΟΥ came to be pronounced , Υ having meanwhile moved to . By about 200 BC, a system of diacritical marks was invented, representing the tone accents in use in Ancient Greek. This also helped to indicate the length of the vowels Α, Ι, and Υ in certain cases
Seventh Letter was any letter from them to Plato, he says. Nevertheless, the "Seventh Letter" has recently been argued to be spurious by prominent scholars such as Malcolm Schofield, Myles Burnyeat, George Boas, Terence Irwin, and Julia Annas. According to Annas, the "Seventh Letter" is "such an unconvincing production that its acceptance by many scholars is best seen as indicating the strength of their desire to find, behind the detachment of the dialogues, something, no matter what, to which Plato is straightforwardly committed." The "Seventh Letter" touches upon a variety of themes, not always in an organized fashion. This article follows Bury