Lorenzo entered the priesthood in 1431, seeking a position as a secretary in the Vatican's diplomatic office. Failing to secure that position, he went to Pavia to lecture, but he got himself in trouble there by offending the greatest jurist and expert on Roman law, Bartolus de Saxoferrato, by criticizing his Latin style. He had to leave Pavia, and became essentially an itinerant lecturer, traveling from city to city seeking opportunities at universities, until he was invited to Rome by Pope Nicholas V to work in Nicholas' new Vatican Library.
With steady employment, he could devote his spare time to writing. He had published in 1433 his first literary work, De Voluptate ("On Pleasure"), in which he argued for the benefit of Epicurus' embracing of natural appetites over the principles of the Stoics. He now produced a text on logic, Repastinatio dialectice et philosophie ("Re-digging dialectic and philosophy"). There are more: Notes on the New Testament, De Elegantis which examined Latin grammar and style, a work on Free Will that argued against Boethius' Consolation of Philosophy.
The truly ground-breaking work, however, was De falso credita et ementita Constantini Donatione declamatio, ("Declamation of the falsely believed and falsified Donation of Constantine") in 1440. The Donation of Constantine was largely believed (argued against, but still believed) as the foundation for papal authority over temporal lords.
Lorenzo took a close look at the text of the document that purported to be a formal imperial decree from the 4th century. His extensive familiarity with the development of Latin over the centuries helped him realize it was written in a style more appropriate to a less-educated writer from the 8th century.
Not only was the language wrong for the premise, he argued three other points:
1. There was no legal authority by which Emperor Constantine could have given Pope Sylvester I the powers claimed in the document.
2. There was no historical evidence in any records that there were administrative changes in the Western Roman Empire.
3. His own doubt that Constantine cared enough about the pope to give him anything.
The Church, understandably, rejected this theory.
Lorenzo was put on trial by the Inquisition in 1444, ostensibly for supporting Alfonso V of Aragon in a territorial dispute over the Papal States.
Lorenzo Valla died 1 August 1457. It did not get formally published until 1517 and became popular among Protestants. Thomas Cromwell had it translated into English in 1534. The Donation eventually became recognized by all as a fake.
So why did I title this with the phrase "Early Modern Scholar"? Shouldn't he be labeled "Renaissance Scholar"? Many historians refer to the Renaissance as "Early Modern" now; the reasons why I look forward to explaining tomorrow.