Montesquieu believed that there were essentially three key ingredients to ensure a republic's success and survival: education, morality and a relatively small geographic boundary. And when it came to morality, Montesquieu didn't hold back on his feelings. Though he admitted to having no personal interest in the validity/invalidity of any given religion (Montesquieu was no theologian), Montesquieu did believe that religion was fundamental to good government, and that some religions were better equipped for certain government systems:
The Christian religion is a stranger to mere despotic power. The mildness so frequently recommended in the Gospel is incompatible with the despotic rage with which a prince punishes his subjects, and exercises himself in cruelty. As this religion forbids the plurality of wives, its princes are less confined, less concealed from their subjects, and consequently have more humanity: they are more disposed to be directed by laws, and more capable of perceiving that they cannot do whatever they please.And Montesquieu got even more specific when he broke down which Christian religions he believed were better fit for certain governments:
While the Mahometan princes incessantly give or receive death, the religion of the Christians renders their princes less timid, and consequently less cruel. The prince confides in his subjects, and the subjects in the prince. How admirable the religion which, while it only seems to have in view the felicity of the other life, continues the happiness of this! It is the Christian religion that, in spite of the extent of the empire and the influence of the climate, has hindered despotic power from being established in Ethiopia, and has carried into the heart of Africa the manners and laws of Europe.
From the characters of the Christian and Mahometan religions, we ought, without any further examination, to embrace the one and reject the other: for it is much easier to prove that religion ought to humanise the manners of men than that any particular religion is true. It is a misfortune to human nature when religion is given by a conqueror. The Mahometan religion, which speaks only by the sword, acts still upon men with that destructive spirit with which it was founded.
When a religion is introduced and fixed in a state, it is commonly such as is most suitable to the plan of government there established; for those who receive it, and those who are the cause of its being received, have scarcely any other idea of policy than that of the state in which they were born.In other words, the Catholic version of Christianity is best for monarchies, while Protestant/Calvin faiths are suited to republics...or so says Montesquieu.
When the Christian religion, two centuries ago, became unhappily divided into Catholic and Protestant, the people of the north embraced the Protestant, and those of the south adhered still to the Catholic. The reason is plain: the people of the north have, and will for ever have, a spirit of liberty and independence, which the people of the south have not; and therefore a religion which has no visible head is more agreeable to the independence of the climate than that which has one. In the countries themselves where the Protestant religion became established, the revolutions were made pursuant to the several plans of political government. Luther having great princes on his side would never have been able to make them relish an ecclesiastical authority that had no exterior pre-eminence; while Calvin, having to do with people who lived under republican governments, or with obscure citizens in monarchies, might very well avoid establishing dignities and preferments.
And while we could debate Montesquieu's understanding of Christianity, Islam, etc., the point I am trying to make is that Montesquieu, and the founders who quoted him, believed religion was as indispensable to republicanism as were the separation of powers (also a Montesquieu idea). And several of the founders actually appear to agree with Montesquieu's belief that Christianity was the best fit for their republican experiment:
"I have examined all religions, as well as my narrow sphere, my straightened means, and my busy life, would allow; and the result is that the Bible is the best Book in the world. It contains more philosophy than all the libraries I have seen."Now let's be careful here. These quotes are NOT proof that the Founding Fathers wanted to establish a Christian nation. Instead, they illustrate that the founders upheld Christianity (what brand of Christianity is another debate for another day) above other forms of worship as the best means by which morality and virtue could be preserved; a component of republican society which they believed was of the utmost importance.
~John Adams to Thomas Jefferson, December 25, 1813.
"Let divines and philosophers, statesmen and patriots, unite their endeavors to renovate the age by impressing the minds of men with the importance of educating their little boys and girls, inculcating in the minds of youth the fear and love of the Deity...and leading them in the study and practice of the exalted virtues of the Christian system."
" Without morals a republic cannot subsist any length of time; they therefore who are decrying the Christian religion, whose morality is so sublime and pure...are undermining the solid foundation of morals, the best security for the duration of free governments."
~Charles Carroll to James McHenry, November 4, 1800.
"God who gave us life gave us liberty. And can the liberties of a nation be thought secure when we have removed their only firm basis, a conviction in the minds of the people that these liberties are a gift from God? That they are not to be violated but with His wrath? Indeed I tremble for my country when I reflect that God is just, and that His justice cannot sleep forever."
~Thomas Jefferson, Notes on the State of Virginia, Query XVIII, 1781.
Of course, this same desire to ensure virtue and morality caused many Christian zealots, then and now, to go beyond the mark:
"Whether our religion permits Christians to vote for infidel rulers is a question which merits more consideration than it seems yet to have generally received either from the clergy or the laity. It appears to me that what the prophet said to Jehoshaphat about his attachment to Ahab ["Shouldest thou help the ungodly and love them that hate the Lord?" 2 Chronicles 19:2] affords a salutary lesson."As with any new idea, a few overzealous, misinformed and even ignorant individuals have (and continue to) poison(ed) the well of understanding, causing scores of historically illiterate followers to believe in a false reality.
~The Correspondence and Public Papers of John Jay, 1794-1826.
It is apprehended that Jews, Mahometans (Muslims), pagans, etc., may be elected to high offices under the government of the United States. Those who are Mahometans, or any others who are not professors of the Christian religion, can never be elected to the office of President or other high office, [unless] first the people of America lay aside the Christian religion altogether, it may happen. Should this unfortunately take place, the people will choose such men as think as they do themselves.
~Governor Samuel Johnston, July 30, 1788 at the North Carolina Ratifying Convention.
"The great misunderstanding of ‘the separation of church and state’ is closer in spirit and letter of the law to the old Soviet Union than it is to the spirit, letter of the law, and actions of the founders of this country."
~D. James Kennedy, What If America Were a Christian Nation Again? (Nashville: Thomas Nelson Publishers, 1982), 5.
"They [the founders] were quite clear that we would create laws based on the God of the Bible and the 10 Commandments."
~David Barton, America’s Godly Heritage (Aledo, TX: Wallbuilders Publishing, 1993), 36.
And though Montesquieu's ideas on religion may seem biased and even a little racist, there is no doubt that they played an important role (along with many of his other ideas) in the development of American republicanism.