It is to please citizens so dangerous that sovereigns mingle in theological questions, take the part of those who succeed in seducing them, persecute all those who do not submit, proscribe with fury the friends of reason, and by repressing knowledge injure their own power. Because the priests, who urge princes to sacrilege when they combat for them, are indignant against the same princes when they refuse to destroy the enemies of their own particular clerical body. They likewise denounce sovereigns as impious if the latter treat theological disputes with the indifference they merit.
When hereafter, reclaimed from their prejudices, princes wish to govern for the good of all, let them cease to hear the interested and often sanguinary councils of these pretended divine men, who, regarding themselves as the centre of all things, wish to have sacrificed for this object the happiness, the repose, the riches, and the honors of the state. Let the sovereign never enter into their dissensions, let him never persecute for religious opinions, which, among sectaries, are commonly on both sides equally ridiculous and destitute of foundation. They would never involve the government if the sovereign had not the weakness to mingle in them. Let him give unlimited freedom to the course of thinking, while he directs by just laws the course of acting on the part of his subjects. Let him permit every one to dream or speculate as he pleases, provided he conducts himself otherwise as an honest man and a good citizen. At least let the prince not oppose the progress of knowledge, which alone is capable of extricating his people from ignorance, barbarity, and superstition, which have made victims of so many Christian rulers. Let him be assured that enlightened and instructed citizens are more law-abiding, industrious, and peaceable than stupid slaves without knowledge and without reason, who will always be ready to take all the passions with which a fanatic wishes to inspire them.
Let the sovereign especially occupy himself with the education of his subjects, nor leave the clergy unobstructedly to impregnate his people with mystic notions, foolish reveries, and superstitious practices, which are only proper for fanatics. Let him at least counterbalance the inculcation of these follies by teaching a morality conformable to the good of the state, useful to the happiness of its members, and social and reasonable. This morality would inform a man what he owed to himself, to society, to his fellow-citizens, and to the magistrates who administered the laws. This morality would not form men who would hate each other for speculative opinions, nor dangerous enthusiasts, nor devotees blindly submissive to the priests. It would create a tranquil, intelligent, and industrious community; a body of inhabitants submissive to reason and obedient to just and legitimate authority. In a word, from such morality would spring virtuous men and good citizens, and it would be the surest antidote against superstition and fanaticism.