Engels, in his lifelong contacts with leaders of Social Democratic and Communist parties in Europe as well as the founders of the First International (the 19th century political union of communist movements), urged them to disseminate and cultivate atheism.[29] He also called for scientific education on a massive scale in order to overcome the fears and illusions of people who required a religious explanation for the world around them. He believed that science would provide an explanation for things that people had formerly required religious concepts to fulfill, and by providing this explanation, people would no longer feel a need to have religion for this purpose. He wrote much about contemporary great scientific discoveries and used them to support the principles of dialectical materialism in all his popular works intended for the ordinary masses in the Communist movements.