Such are some of the main features of the Bogomilian heresy, as they have come down to us, to a great extent, from the writings of their bitterest opponents. Nor will anyone marvel that these doctrines should have spread as they did among those Sclavonic races, who acted as the missionaries of the first Reformation in Western Europe. It can hardly be considered fanciful if we detect certain remarkable analogies between the belief and observances of the Bogomiles and the primitive institutions, and even the heathen religion, of the Sclaves. It has already been mentioned that the Manichæan conversion began among the Bulgarians when they were still to a great extent pagan. The same is true with regard to the spread of the Bogomilian heresy among the Serbs, with whom heathendom held its own in parts till the thirteenth century.[37] A remarkable uniformity presents itself in the languages, beliefs, and institutions of all Sclavonic nations; and if we may assert, from the analogy of the Baltic Sclaves, that the Bulgarians and Serbs also divided their worship between their Black God or Spirit of Evil, and their White God or Spirit of Good, it follows that the Manichæan missionaries found the dualistic theology, which lies at the bottom of so much of their doctrine, already existing among the people they wished to convert;[38] while the propagandists of orthodoxy must have discovered to their vexation that the Sclavonic mind had been trained by superstition, as well as by what mother-wit it possessed, to rebel against their stupendous dogma, that an All-powerful Spirit of Good could create and tolerate the Spirit of Evil. Our Presbyter Cosmas notices that this difficulty presented itself, even to the ‘orthodox’ Bulgarians, and so lost is he in indignation at these profane inquiries as to the devil’s paternity, that he forgets to answer them.