letter - quotes

Arthur Schopenhauer, 1788-1860

was a German philosopher

If you want to know your true opinion of someone, watch the effect produced in you by the first sight of a letter from him.

Plato, ca. 427 BC-ca. 347 BC

was a Greek author and philosopher in Athens

[About letters] For this invention of yours will produce forgetfulness in the minds of those who learn it, by causing them to neglect their memory, inasmuch as, from their confidence in writing, they will recollect by the external aid of foreign symbols, and not by the internal use of their own faculties. Your discovery, therefore, is a medicine not for memory, but for recollection-for recalling to, not for keeping in mind.

( The PhAbdrus, Lysis, and Protagoras of Plato: A New and Literal Translation, p 85-86 )