Tacitus and Suetonius alike seem to have collected their information from three chief sources, private memoirs, popular rumours, in which are to be included pasquinades and the topical songs of actors, and the official record of the transactions of the Senate. The first two sources of information are obviously not of a trustworthy character; memoirs are not to be relied on even in these days of rapid transmission of news and wide publicity. An historian who should essay to compile the biography of a public man of today, even from the daily and weekly journals which are filled with personal gossip about those upon whom the attention of the public is fixed, would find such a mass of contradictions to deal with that he would abandon his task in despair; and yet the matter thus afforded to his inspection is day by day subject to correction. Memoirs written by an irresponsible person in his private study are even more likely to contain perversions of fact, to omit, to exaggerate, to represent exclusively the personal bias of the writer. It is hardly necessary to add that loose anecdotes and the buffooneries of actors do not constitute evidence; it is, indeed, difficult to understand how Suetonius, a presumably grave schoolmaster, could quote snatches of popular songs as serious history, and repeat the filthy gossip of the Roman streets. But the evidence of public documents such as the record of the transactions of the Senate is unimpeachable; and this evidence, whenever Tacitus gives it us, is invariably such as to compel us to believe that Tiberius was a wise and moderate ruler.