This thesis is a translation and study of the Italian Jesuit, Ippolito Desideri's Tibetan manuscript The Essence of the Christian Faith which he wrote towards the end of his five year stay in Tibet (1716-1721). It is the first of his Tibetan works to be translated into English. Desideri's intention in writing was twofold: Firstly, to explain to Tibetan Buddhist readers why their denial of an intrinsically existent God (rang grub dkon mchog) leads to nihilism. Secondly, he wrote to express in the Tibetan language (in the form of a catechism) something of the nature and character of the triune God, and why belief in him does not destroy the Buddhist understanding of 'emptiness', but in fact enhances it. In Desideri's introduction he explains why he considers the Tibetan Buddhist dGe lugs presentation of 'emptiness' to be flawed. He disagrees with their asseliion that all things are beginngless and are mere mentally fabricated constructs which are dependent on their 'basis of designation'. Desideri considers that the existence of the Independent, who is external to the inter-dependent, explains the existence of the inter-dependent; whereas the denial of the Independent leads to the denial of everything. Desideri describes God as the all pervading and compassionate One who sent his Son to liberate people from that which causes them to be shackled and which only perpetuates their 'ignorance' . Drawing on many highly contextualised illustrations, he presents the main doctrines of the Christian Faith in a way that a Tibetan reader who was hearing about Christianity for the first time could relate to. Desideri sought to reassure his readers the acceptance of the biblical God who necessarily exists intrinsically would not destroy, but would in fact enhance, the dGe lugs understanding of 'emptiness' and thereby remove the 'fall into nihilism'.