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"Lucius Calpurnius Piso Caesoninus", in Wikipedia.

Lucius Calpurnius Piso Caesoninus (c. 100 BC – 43 BC) was a Roman statesman and the father-in-law of Julius Caesar through his daughter Calpurnia Pisonis. He also had a son, Lucius Calpurnius Piso, known as “the Pontifex”, who was Consul in 15 BC. He was reportedly a follower of a school of Epicureanism that had been modified to befit politicians, as Epicureanism itself favored withdrawal from politics.

In 58 BC, when consul, Piso and his colleague, Aulus Gabinius, entered into a compact with Publius Clodius, with the object of getting Marcus Tullius Cicero out of the way. Piso’s reward was the province of Macedonia, which he administered from 57 BC to the beginning of 55 BC, when he was recalled and the province was given to Quintus Ancharius. Piso’s recall was perhaps in consequence of the violent attack made upon him by Cicero in the Senate in his speech “De provinciis consularibus”.

Caesar mentions his father-in-law in his Gallic Commentaries. Piso’s grandfather, also named L. Calpurnius Piso, was killed by the same Gauls that Caesar would later conquer.

On his return, Piso addressed the Senate in his defence, and Cicero replied with the coarse and exaggerated invective known as “In Pisonem”. Piso issued a pamphlet by way of rejoinder, and there the matter ended. Cicero may have been afraid to bring the father-in-law of Julius Caesar to trial. At the outbreak of the civil war, Piso offered his services as mediator. However, when Caesar marched upon Rome, he left the city by way of protest of Caesar. Piso did not openly declare support for Gnaeus Pompeius Magnus and remained neutral but is widely believed he secretly supported Pompey but still did not forfeit the respect of Caesar when Pompey was defeated.

After the murder of Caesar, Piso insisted on the provisions of Caesar’s will being strictly carried out and, for a time, he opposed Mark Antony. Subsequently, he became one of Anthony’s supporters and is mentioned as taking part in an embassy to Antony’s camp at Mutina with the object of bringing about a reconciliation with Octavian.

He is believed to have been the owner of the Villa of the Papyri at Herculaneum.

The maxim fiat justitia ruat caelum (“let justice be done, though the heavens fall”), used by Lord Mansfield in Somerset’s Case and in reversing the outlawry of John Wilkes, and in the alternate form fiat iustitia, et pereat mundus by Ferdinand of Habsburg, is sometimes attributed to Piso (more often to Gnaeus Calpurnius Piso), but this is disputed.


Chisholm, Hugh, ed. (1911). Encyclopædia Britannica (11th ed.). Cambridge University Press.

William, Smith, ed. (1849). Dictionary of Greek and Roman Biography and Mythology. Boston: C.C. Little and J. Brown. OCLC 656753050

For a survey of Roman Epicureans active in politics, see Arnaldo Momigliano, review of Science and Politics in the Ancient World by Benjamin Farrington (London 1939), in Journal of Roman Studies 31 (1941), pp. 151–157.

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