Editing Avicenna (section)

=== ''Liber Primus Naturalium'' ===
Avicenna considered whether events like rare diseases or disorders have natural causes.<ref>Avicenna Latinus. 1992. Liber Primus Naturalium: Tractatus Primus, De Causis et Principiis Naturalium. Leiden (The Netherlands): E.J. Brill.</ref> He used the example of [[polydactyly]] to explain his perception that causal reasons exist for all medical events. This view of medical phenomena anticipated developments in the [[Age of Enlightenment|Enlightenment]] by seven centuries.<ref>Axel Lange and [[Gerd B. Müller]]. Polydactyly in Development, Inheritance, and Evolution. The Quarterly Review of Biology Vol. 92, No. 1, Mar. 2017, pp. 1–38. {{doi|10.1086/690841}}.</ref>