because we are ignorant of our true nature. So what is called the primordial Buddha, or Adibuddha, is only a metaphor for our true condition. Regarding the term Adi-Buddha as used in the tantric Kalachakra tradition, Vesna Wallace notes:when the Kalacakra tradition speaks of the Adibuddha in the sense of a beginningless and endless Buddha, it is referring to the innate gnosis that pervades the minds of all sentient beings and stands as the basis of both samsara and nirvana. Whereas, when it speaks of the Adibuddha as the one who first attained perfect enlightenment by means of imperishable bliss, and when it asserts the necessity of acquiring merit and knowledge in order to attain perfect Buddhahood, it is referring to the actual realization of one's own innate gnosis. Thus, one could say that in the Kalacakra tradition, Adibuddha refers to the ultimate nature of one's own mind and to the one who has realized the innate nature of one's own mind by means of purificatory practices. Modern Buddhist anti-theism The modern era brought Buddhists into contact with the Abrahamic religions, especially Christianity. Attempts to convert Buddhist nations to Christianity through missionary work were countered by Buddhist attempts at refutations of Christian doctrine and led to the development of Buddhist Modernism. The earliest Christian attempts to refute Buddhism and criticize its teachings were those of Jesuits like Alessandro Valignano, Michele Ruggieri, and Matteo Ricci. These attacks were answered by Asian Buddhists, who wrote critiques of Christianity, often centered on refuting Christian theism. Perhaps the earliest such attempt was that of the Chinese monk Zhu Hong (祩宏, 1535–1615), who authored Four Essays on Heaven (天說四端). Another influential Chinese Buddhist critic of Christian theism was Xu Dashou (許大受), who wrote a long and systematic refutation of Christianity, titled Zuopi (佐闢 , Help to the refutation), which attempts to refute Christianity from the point of view of three Chinese traditions (Confucianism, Buddhism, and Taoism). The monk Ouyi Zhixu (蕅益智旭, 1599–1655) later wrote the Bixie ji ("Collected Essays Refuting Heterodoxy"), which specifically attacks Christianity on the grounds of theodicy as well as relying on classical Confucian ethics. According to Beverley Foulks, in his essays, Zhixu "objects to the way Jesuits invest God with qualities of love, hatred, and the power to punish. He criticizes the notion that God would create humans to be both good and evil, and finally he questions why God would