His most important work was the five book Gargantua and Pantagruel ; however it is unclear whether all of the fifth book was written by Rabelais himself. Within, although some chapters consist entirely of lists of vulgarities, a number of political and religious themes are considered, amongst them being:
- Proper methods of education. (Book 1)
- The Abbey of Theleme - a Utopian monastery, wherein customs were the exact opposite of the solemn, austere and strictly-regulated ones followed in typical monastic environments, and the primary commandment was "Do what thou wilt." (Book 1)
- The absurdities of the legal system, and how the only way to finally resolve a dispute is to drag it out until both parties are sick of it. (Books 2, 5)
- Methods of divination (Book 3)
- Reasons for and against marriage. (Books 4-5)
Some of the topics explored by Rabelais were controversial, and only the support of influential patrons preserved him from severe ecclesiastical censure during his lifetime; the third and fourth books of Gargantua and Pantagruel were both banned at times. The adjective, Rabelaisian, from his name, describes something that is in the style of his writings: containing an abundance of coarse humor, extravagant language and keen satire.
The works of Rabelais were the subject of study by the Russian cultural theorist M. M. Bakhtin (1885-1975), who derived two major concepts from "Gargantua and Pantagruel": that of the carnivalesque, mocking authority through proletarian laughter; and of the grotesque body, seeing the greatest reality in the portrayal of bodily functions, principally sexual and excretory. The emphasis on anti-authoritarianism may explain why his work on the subject, Rabelais and his World, while submitted as a PhD thesis in the early 1940s, was not passed for a doctorate and was only published in the post-Stalinist (relative) thaw of 1965; though it is quite possible that Bakhtin, who smoked the only manuscript of his study of the German novel during the battle of Stalingrad , did not consider publication a matter of any urgency.