He is generally credited with the invention of the kana, but there is apparently some doubt about this story amongst scholars. This mantra-based theory of language had a powerful effect on Japanese thought and society which up until Kūkai's time had been dominated by imported Chinese culture of thought, particularly in the form of the Classical Chinese language which was used in the court and amongst the literati, and Confucianism which was the dominant political ideology. In particular, Kūkai was able to use this new theory of language to create links between indigenous Japanese culture and Buddhism. For instance, he made a link between the Buddha Mahavairocana and the Shinto sun Goddess Amaterasu. Since the emperors were thought to be descended form Amaterasu, Kūkai had found a powerful connection here that linked the emperors with the Buddha, and also in finding a way to integrate Shinto with Buddhism, something that had not happened with Confucianism. Buddhism then became essentially an indigenous religion in a way that Confucianism had not. And it was through language and mantra that this connection was made. Kūkai helped to elucidate what mantra is in a way that had not been done before: he addresses the fundamental questions of what a text is, how signs function, and above all, what language is. In this, he covers some of the same ground as modern day Structuralists and others scholars of language, although he comes to very different conclusions. In this system of thought, all sounds are said to originate from "a" – which is the short "a" sound in father. For esoteric Buddhism "a" has a special function because it is associated with Shunyata or the idea that no thing exists in its own right, but is contingent upon causes and conditions. (See Dependent origination) In Sanskrit "a" is a prefix which changes the meaning of a word into its opposite, so "vidya" is understanding, and "avidya" is ignorance (the same arrangement is also found in many Greek words, like e.g. "atheism" vs. "theism" and "apathy" vs. "pathos"). The letter a is both visualised in the Siddham script and pronounced in rituals and meditation practices. In the Mahavairocana Sutra which is central to Shingon Buddhism it says: Thanks to the original vows of the Buddhas and Bodhisattvas, a miraculous force resides in the mantras, so that by pronouncing them one acquires merit without limits". [in Conze, p. 183]  A mantra is Kuji-kiri in Shugendo.