Alberts writings collected in 1899 went to thirty-eight volumes. These displayed his prolific habits and encyclopedic knowledge of topics such as logic, theology, botany, geography, astronomy, astrology, mineralogy, alchemy, zoology, physiology, phrenology, justice, law, friendship, and love. He digested, interpreted, and systematized the whole of Aristotles works, gleaned from the Latin translations and notes of the Arabian commentators, in accordance with Church doctrine. Most modern knowledge of Aristotle was preserved and presented by Albert.
His principal theological works are a commentary in three volumes on the Books of the Sentences of Peter Lombard (Magister Sententiarum), and the Summa Theologiae in two volumes. The latter is in substance a more didactic repetition of the former.
Alberts activity, however, was more philosophical than theological (see Scholasticism). The philosophical works, occupying the first six and the last of the 21 volumes, are generally divided according to the Aristotelian scheme of the sciences, and consist of interpretations and condensations of Aristotles relative works, with supplementary discussions upon contemporary topics, and occasional divergences from the opinions of the master. Albert believed that Aristotle's approach to natural philosophy did not pose any obstacle to the development of a Christian philosophical view of the natural order.
Alberts knowledge of natural science was considerable and for the age remarkably accurate. His industry in every department was great: not only did he produce commentaries and paraphrases of the entire Aristotelian corpus, including his scientific works, but Albert also added to and improved upon them. His books on topics like botany, zoology, and minerals included information from ancient sources, but also results of his own empirical investigations. These investigations pushed several of the special sciences forward, beyond the reliance on classical texts. In the case of embryology, for example, it has been claimed that little of value was written between Aristotle and Albert, who managed to identify organs within eggs. Furthermore, Albert also effectively invented entire special sciences, where Aristotle has not covered a topic. For example, prior to Albert, there was no systematic study of minerals. For the breadth of these achievements, he was bestowed the name Doctor Universalis.'
Much of Alberts empirical contributions to the natural sciences have been superseded, but his general approach to science may be surprisingly modern. For example, in De Mineralibus' (Book II, Tractate ii, Ch. 1) Albert claims, "For it is [the task] of natural science not simply to accept what we are told but to inquire into the causes of natural things."