From the Wikipedia entry on A Letter Concerning Toleration by John Locke, published in 1689.
Unlike Hobbes, who saw uniformity of religion as the key to a well-functioning civil society, Locke argues that more religious groups actually prevent civil unrest. Locke argues that civil unrest results from confrontations caused by any magistrate’s attempt to prevent different religions from being practiced, rather than tolerating their proliferation. Locke’s primary goal is to “distinguish exactly the business of civil government from that of religion.” He makes use of extensive argument from analogy to accomplish his goal, and relies on several key points. The thing that he wants to persuade the reader of is that government is instituted to promote external interests, relating to life, liberty, and the general welfare, while the church exists to promote internal interests, i.e., salvation. The two serve separate functions, and so, must be considered to be separate institutions…
Locke argued that atheists should not be tolerated because ‘Promises, covenants, and oaths, which are the bonds of human society, can have no hold upon an atheist’. The Roman Catholic Church can not be tolerated either, according to Locke, because ‘all those who enter into it do thereby ipso facto deliver themselves up to the protection and service of another prince’. If this Church was tolerated, a magistrate would have to abide by the settling of a ‘foreign jurisdiction’ in his own country and see its followers ‘listed, as it were, for soldiers against his own Government’.
Toleration is central to Locke’s political philosophy. Consequently, only churches that teach toleration are to be allowed in his society. [Wikipedia]
From “I’m Right, You’re Wrong, Go To Hell”, by Bernard Lewis, in The Atlantic Monthly, May 2003.
Tolerance is, of course, an extremely intolerant idea, because it means “I am the boss: I will allow you some, though not all, of the rights I enjoy as long as you behave yourself according to standards that I shall determine.” That, I think, is a fair definition of religious tolerance as it is normally understood and applied. In a letter to the Jewish community of Newport, Rhode Island, that George Washington wrote in 1790, he remarked, perhaps in an allusion to the famous “Patent of Tolerance” promulgated by the Austrian Emperor Joseph II a few years previously, “It is now no more that toleration is spoken of, as if it was by the indulgence of one class of people that another enjoyed the exercise of their inherent natural rights.” At a meeting of Jews, Christians, and Muslims in Vienna some years ago the Cardinal Archbishop Franz Koenig spoke of tolerance, and I couldn’t resist quoting Washington to him. He replied, “You are right. I shall no more speak of tolerance; I shall speak of mutual respect.” There are still too few who share the attitude expressed in this truly magnificent response.
For those taking the relativist approach to religion (in effect, “I have my god, you have your god, and others have theirs”), there may be specific political or economic reasons for objecting to someone else’s beliefs, but in principle there is no theological problem. For those taking the triumphalist approach (classically summed up in the formula “I’m right, you’re wrong, go to hell”), tolerance is a problem. Because the triumphalist’s is the only true and complete religion, all other religions are at best incomplete and more probably false and evil; and since he is the privileged recipient of God’s final message to humankind, it is surely his duty to bring it to others rather than keep it selfishly for himself. [The Atlantic Monthly]