One of the main allusions that Locke makes throughout his work is to Richard Hooker’s Of the Lawes of Ecclesiastical Politie—a defense of the Anglican church against the supposed corruption of Roman Catholicism. Hooker and Locke both explore, at length, the natural inclinations of humanity (“man in nature”) and the effect of divine law on human self-government.
Locke introduces the reader to Hooker's writing at the beginning of his Second Treatise, in the opening pages of Chapter 2, as he discusses the "state of nature" of humanity and the fundamental equality between human beings:
This equality of men by nature, the judicious Hooker looks upon as so evident in itself, and beyond all question, that he makes it the foundation of that obligation to mutual love amongst men, on which he builds the duties they owe one another, and from whence he derives the great maxims of justice and charity.
Locke continues with an extensive quote from Hooker's Lawes, the first of many such quotations in the Second Treatise of Government. As the above passage suggests, Locke owes much of his vision for human nature, and his political philosophy that results from this vision, to the works and authors that explored similar themes before him. Locke invites many of these sources, from Hooker to the Holy Bible, into his scholarly conversation in the Second Treatise, thereby ensuring both its legitimacy as a work of considerable academic rigor and its digestibility by readers who might be familiar with scripture and the work of Locke's predecessors and peers.
Locke’s Second Treatise has no shortage of allusions—to philosophers and political theorists who preceded Locke and influenced his thought, and also, first and foremost, to the Bible. In this passage from Chapter 2, Locke quotes directly from the book of Genesis:
…and upon this is grounded that great law of nature, Whoso sheddeth man’s blood, by man shall his blood be shed. And Cain was so fully convinced, that every one had a right to destroy such a criminal, that after the murder of his brother, he cries out, Every one that findeth me, shall slay me; so plain was it writ in the hearts of all mankind.
The line “Whoso sheddeth man’s blood, by man shall his blood be shed" is a direct quote from God's address to Noah in Chapter 9 of the Book of Genesis, in the Old Testament, while the reference to Cain and Cain's murder of his brother alludes to the story of Cain and Abel from Chapter 4 of Genesis.
Locke is absolutely clear that his vision of law and human nature is entirely predicated on the Bible, and a consistent drip of biblical allusion ensures that this point comes across throughout the Second Treatise. In this passage, Locke takes influence from God's command and the story of Cain and Abel to understand questions of punishment and justice in the aftermath of violence or wrongdoing: “by the same reason,” Locke continues, “may a man in the state of nature punish the lesser breaches of that law.” In other words, just as Cain sought ultimate retribution for his own sin according to divine law, Locke sees that any man is naturally inclined (and justified) in punishing another man proportionately for their crimes.
In Chapter 8, Locke explores the origins of civilization and the formations of early governments. To understand how "political society" evolved, he uses allusion to draw on the work of Josephus Acosta, a Spaniard who wrote extensively on Spanish discoveries and indigenous populations in South America in the 17th century:
And if Josephus Acosta’s word may be taken, he tells us, that in many parts of America there was no government at all. There are great and apparent conjectures, says he, that these men, speaking of those of Peru, for a long time had neither kings nor common-wealths, but lived in troops, as they do this day in Florida, the Cheriquanas, those of Brazil, and many other nations, which have no certain kings, but as occasion is offered, in peace or war, they choose their captains as they please…
By invoking Acosta's work, which examined societies in the Americas that had developed apart from those of Europe and that therefore had different societal structures and forms of government, Locke reflects on the nature of government and whether humanity has a natural inclination towards any particular form of self-organization. The civilizations in Acosta's writing are examples of how government can spring up through "voluntary union" and "mutual agreement from men"—proving Locke's larger point that human nature does not necessarily lend itself to autocracy or to imposition of order by an absolute monarch.
