[5] In his historical writings, Gelli was influenced by the late 15th-century forgeries of Annio da Viterbo, which purported to provide evidence from ancient texts to show that Tuscany had been founded by Noah and his descendants after the Deluge.

Gelli wrote two comedies (La sporta, 1543; L'errore, 1556), a few poems, and a Trattatello sull'origine di Firenze, but his most significant works are two treatises in dialogue form.

Ten reject the prospect of returning to their human lives, but the elephant, who had been a philosopher, accepts Odysseus's view; the last dialogue celebrates the nobility of man's intellect.

Lastly, he published several letters upon Dante’s Inferno, entitled Ragionamento sopra le Difficultà del mettere in Regole la nostra lingua, without date.

Gelli supports his theory by pointing out names of places such as Carrara, Arignano, Arezzo, Fiesole, by asserting that there are many Florentine words which are derivatives of Aramaic and Hebrew.

In addition to linguistic sources he also claims as evidence for his hypothesis folklore material as well as remains of ancient structures such as temples, aqueducts, bridges, tombs, and so forth.

In his treatise Gelli emphasizes the cyclical feature of historical development, vaguely foreshadowing Vico, and maintains that when the civilization of a people has reached its peak it declines to its original state and then starts all over again.

[12] Gelli's theories not only aroused the objective criticism of Vincenzo Borghini,[13] but they provoked dissension among the members of the Accademia Fiorentina during the early years of its history.

The most harsh among the opponents of Gelli and his followers, known as gli Aramei, was the Florentine scholar and writer Antonio Francesco Grazzini.