Smart's early work involved linguistic analysis, in which he had trained at Oxford. Later, he said that this came close to "cross-cultural study" but had stopped short, since he was still too captive to "our language" and "various assumptions of our culture". However, when he came to publish this he included later conceptual ideas, expanding his dissertation. Interested in Rudolf Otto's concept of the Holy as a key to understanding religion, he found this too restrictive, since Buddhism is non-theistic. Instead, he suggested that religious experience can be either numinous or mystical. He was also influenced by R.C. Zaehner's interest in mysticism, having consulted him at Oxford. He then examined what he took as key religious concepts, such as revelation, faith, conversion and knowledge and analysed what these meant in Christianity, Hinduism, and Buddhism without evaluating any belief in terms of truth or falsity. He was consciously attempting to break out of captivity to Western modes of thought so that for example theism is not taken as an essential component of religion, thus such ideas as theophany or a single ultimate focus or sacrifice do not necessarily translate from the Christian into other religious contexts. "She who knows but one religion knows none," said Smart. Western concern for doctrine overlooked the importance of religious experience. Early in his career, he insisted that an ideology such as Marxism as well as nationalism and rationalism could be considered religious, because they resemble religious traditions in how they function, and therefore properly belong to Religious Studies, the subject matter of which was "non-finite".