Lullus' Quattuor libri principiorum were developed from
the Ars compendiosa inueniendi ueritatem. They were
probably written in the period ca. 1274-1283. In these four
books we find the main rules of Lullian Art in an early stage,
as a muster of Lullus'universal knowledge system. These books are
here set together to show the unity of method for theology,
philosophy and justice. The traditional matters about medicine are
explained with the existing logical constraints taken into account.
The chapters on generation and corruption, fever, urine and pulse
show the current theory of humours and the optimal levels of the
four natural elements, preventive treatments, and the means to
recover from illness. The book Principia medicinae is the
only one that has parallel textual Catalan tradition.