A universal religion does not exist. The closest we came to universality was paganism. The common thread was there are no rules. It could be said paganism is a universal religion.
Divinity has revealed itself in the different parts of our globe in a manner of such little uniformity, that in matters of religion men look upon each other with hatred and disdain. The partisans of the different sects see each other very ridiculous and foolish. The most respected mysteries in one religion are laughable for another. God, having revealed Himself to men, ought at least to speak in the same language to all, and relieve their weak minds of the embarrassment of seeking what can be the religion which truly emanated from Him, or what is the most agreeable form of worship in His eyes.
A universal God ought to have revealed a universal religion. By what fatality are so many different religions found on the earth? Which is the true one amongst the great number of those of which each one pretends to be the right one, to the exclusion of all the others? We have every reason to believe that not one of them enjoys this advantage. The divisions and the disputes about opinions are indubitable signs of the uncertainty and of the obscurity of the principles which they profess.