structural:summarization
In England (1637–1641)

Hobbes came back home from Paris, in 1637, to a country riven with discontent, which disrupted him from the orderly execution of his philosophic plan. However, by the end of the Short Parliament in 1640, he had written a short treatise called The Elements of Law, Natural and Politic. It was not published and only circulated as a manuscript among his acquaintances. A pirated version, however, was published about ten years later. Although it seems that much of The Elements of Law was composed before the sitting of the Short Parliament, there are polemical pieces of the work that clearly mark the influences of the rising political crisis. Nevertheless, many (though not all) elements of Hobbes's political thought were unchanged between The Elements of Law and Leviathan, which demonstrates that the events of the English Civil War had little effect on his contractarian methodology. However, the arguments in Leviathan were modified from The Elements of Law when it came to the necessity of consent in creating political obligation: Hobbes wrote in The Elements of Law that Patrimonial kingdoms were not necessarily formed by the consent of the governed, while in Leviathan he argued that they were. This was perhaps a reflection either of Hobbes's thoughts about the engagement controversy or of his reaction to treatises published by Patriarchalists, such as Sir Robert Filmer, between 1640 and 1651.

When in November 1640 the Long Parliament succeeded the Short, Hobbes felt that he was in disfavour due to the circulation of his treatise and fled to Paris. He did not return for 11 years. In Paris, he rejoined the coterie around Mersenne and wrote a critique of the Meditations on First Philosophy of Descartes, which was printed as third among the sets of "Objections" appended, with "Replies" from Descartes, in 1641. A different set of remarks on other works by Descartes succeeded only in ending all correspondence between the two.

Hobbes also extended his own works in a way, working on the third section, De Cive, which was finished in November 1641. Although it was initially only circulated privately, it was well received, and included lines of argumentation that were repeated a decade later in Leviathan. He then returned to hard work on the first two sections of his work and published little except a short treatise on optics (Tractatus opticus), included in the collection of scientific tracts published by Mersenne as Cogitata physico-mathematica in 1644. He built a good reputation in philosophic circles and in 1645 was chosen with Descartes, Gilles de Roberval and others to referee the controversy between John Pell and Longomontanus over the problem of squaring the circle.