From these sources we learn that David was a Pantheist. He identified God with the material substratum of all things, "materia prima" (prime matter). He reduced all reality to three categories, namely bodies, minds, and eternal substances. The indivisible substrate or constituent of bodies is matter ("yle"); of minds, or souls, intellect ("nous"); and of eternal substances, God (Deus). These three, matter, intellect, and God, are one and the same. Consequently, all things, material, intellectual, and spiritual, have one and the same essence — God. The phraseology, which must be David's own, as well as the title above mentioned, "De Tomis", suggests the influence of Johannes Scotus Eriugena. Eriugena's work must have been widely known and read in the first decades of the thirteenth century, as is evident from many undeniable facts. Whether David was influenced also by Amalric of Chartres is a matter of debate. Albert, who was a contemporary of David, says that David merely renewed the heresy of someone known as Alexander, "who taught that God and intellect and matter are one substance". It is impossible to determine whom Albert means by Alexander, "a disciple of Xenophanes"; probably the reference is to some Arabian work that went under the name of a Greek philosopher. There were several works of that kind current in the early part of the thirteenth century. Some critics, however, put forward the surmise that David's immediate source was Avicebron's "Fons Vitæ", or the work "De Unitate", written by Archdeacon Gundisalvi of Segovia, who was well versed in Arabian philosophical literature. Whatever the source, the doctrines were pantheistic, as all authorities concur in describing them.