Now Brutus had deliberately assumed a mask to hide his…

““Now Brutus had deliberately assumed a mask to hide his true character.  When he learned of the murder by Tarquin of the Roman aristocrats, one of the victims being his own brother, he had come to the conclusion that the only way of saving himself was to appear in the king's eyes as a person of no account. If there were nothing in his character for Tarquin to fear, and nothing in his fortune to covet, then the sheer contempt in which he was held would be a better protection than his own rights could ever be.  Accordingly he pretended to be a half-wit and made no protest at the seizure by Tarquin of everything he possessed. He even submitted to being known publicly as the 'Dullard' (which is what his name signifies), that under cover of that opprobrious title the great spirit which gave Rome her freedom might be able to bide its time. On this occasion he was taken by Arruns and Titus to Delphi less as a companion than as a butt for their amusement; and he is said to have carried with him, as his gift to Apollo, a rod of gold inserted into a hollow stick of cornel-wood - symbolic, it may be, of his own character. The three young men reached Delphi, and carried out the king's instructions.  That done, Titus and Arruns found themselves unable to resist putting a further question to the oracle.  Which of them, they asked, would be the next king of Rome? From the depths of the cavern came the mysterious answer: 'He who shall be the first to kiss his mother shall hold in Rome supreme authority.' Titus and Arruns were determined to keep the prophecy absolutely secret, to prevent their other brother, Tarquin, who had been left in Rome, from knowing anything about it. Thus he, at any rate, would be out of the running. For themselves, they drew lots to determine which of them, on their return, should kiss his mother first. Brutus, however, interpreted the words of Apollo's priestess in a different way. Pretending to trip, he fell flat on his face, and his lips touched the Earth - the mother of all living things.””

— Livy