I recently stumbled across the very interesting (if you have an interest in Patrology) Tertullian Project, a site run by Roger Pearse, a British software consultant with an interest in Tertullian.
Quintus Septimus Florens Tertullianus is one of the most interesting and tragic figures of patristic times. Born in Carthage in about 160, attracted by the witness of martyrs, he converted to Christianity in 197. His background as a lawyer made him a particularly clear thinker and writer for the Chrsitian cause; amongst his works are apologitics addressed to pagans and Jews, dogmatic polemics against gnostics and heretics and treatises on ethical and aesetical matters. He was the first Latin ecclesiastical writer (remember, Greek was the lingua franca of most Christians, even in Rome) and he contributed literally hundreds of neologisms to express Christian thought in Latin.
However, his legalistic and rigorist approach (typical of North African Christianity) was to be his downfall. He rejected Christian participation in many aspects of Roman society and was notoriously hostile to philosophical thought, posing the question 'What has Athens to do with Jerusalem?' He was unable to accept what he saw as the laxist approach of the institutional church with regards to forgiveness of sins and penance and by 207 was drawn towards Montanism, an early 'charismatic' movement which rejected the institutional church in favour of new prophesies. The 'real' church consisted, not of the bishops and their flocks, but the 'spiritual men' who were uncompromising in their morality. (Curiously, Montanus himself seemingly claimed to be an incarnation of the Holy Spirit.) By 213, Tertullian had totally broken from the institutional church and this coupled with his unorthodox later teaching means that he must be counted amongst the Ecclesiastical Writers rather than the Church Fathers. It's also easy to see traces of what would become Donatism in the thought of Tertullian. However, he rightly deserves his place as one of the great Christian thinkers and as an influence on the North African Christian environment which brought forth St. Augustine. In Tertullian we find the basis for the orthodox formulation of the doctrine of the Trinity and the incarnation. The great St. Cyprian (c.210-258) read his works daily, referring to him as 'The Master'. Tertullian vanishes quietly from history about 220, presumably dying of natural causes.