The link which connects Aristotle, Hippocrates, Galen, Al-Razi, and Ibn Sina all together is through their study of medicine. The Greeks Hippocrates and Aristotle wrote about diseases, methods of observation, while Galen later built upon this with his defining of bodily humors. Much later, Al-Razi would go on to challenge their work, while also expanding upon medicinal literature. Last, Ibn Sina (Avicenna) based his seminal work, The Canon of Medicine, through a blending of the old Greco-Roman findings.
During the Medieval Period, Islamic scholars went to work translating, and thereby also preserving, the knowledge born out of the Greco-Roman era. In 832 CE, Al-Ma’mun established the House of Wisdom in Baghdad, one such center for scholarly learning. But the old texts were more than simply re-copied, they were also re-evaluated. Al-Razi would criticize some of the findings put forth by Galen when he found evidence against them. Sina’s Canon took Greek understanding on Anatomy, diseases, and ethics, and organized them into what would become the standard for medical texts for centuries. Given its practical usefulness, with the added weight of the names of the authors, it may not be surprising to hear that the knowledge of these Classical thinkers has survived well into modern times.