Boethius, 475 AD
Boethius is one of the greatest philosophers of the classical period. Due to some political conflicts, he got arrested and jailed in 522 AD. In prison he wrote his masterpiece “On the Consolation of Philosophy”. Boethius writes the book as a conversation between himself and a female personification of philosophy who visits him in the prison. Philosophy consoles Boethius by discussing the transitory nature of fame and wealth (“no man can ever truly be secure until he has been forsaken by Fortune”), and the ultimate superiority of things of the mind, which she calls the “one true good”. She contends that happiness comes from within, and that virtue is all that one truly has, because it is not imperiled by the vicissitudes of fortune.

Ibn Sina (Avicenna), 980 AD
Ibn Sina is the polymath author of the “The Book of Healing” and “The Canon of Medicine” encyclopedias. The Book of Healing is a scientific and philosophical encyclopedia, and The Canon of Medicine is an encyclopedia of medicine in five books. Ibn Sina’s corpus includes writings on astronomy, alchemy, geography and geology, psychology, Islamic theology, logic, mathematics, physics, and works of poetry.

Floating man (also known as flying man) is one of the thought experiments by Ibn Sina to argue for the existence of the soul. The floating man argument is concerned with one who falls freely in the air. This subject knows himself, but not through any sense perception data. Floating or suspending refers to a state in which the subject thinks on the basis of his own reflection without any assistance from sense perception or any material body. This mind flutters over the abyss of eternity. Similar to the French philosopher Descartes (1596–1650) pointed out the existence of the conscious self as a turning point in epistemology, using the phrase “Cogito ergo sum,” known as “I think, therefore I am” in modern english translation, Ibn Sina had referred to the existence of consciousness in the flying man argument in 11th century (nearly 600 years before Descartes).

Anselm, 1033 AD
Known as the father of the scholastic tradition, Anselm was the philosopher monk of Canterbury. He believed that faith is more valuable than logic, but he wanted to strengthen faith with logical arguments. In his two writings called Monologion (conversation with self), and Proslogion (conversation with others) he introduces two arguments to support the existence of God: (1) cosmological argument, and the highly controversial (2) ontological argument. In cosmological argument, Anselm claims that all the natural things need a greater external power to exist. In ontological argument, Anselm claims that if we accept that God is a being which none greater can be conceived, then God must exists in reality, because if the God is only in our imagination, then a greater god (the God in reality) is imaginable, and that’s contradictory. Philosopher Immanuel Kant (1724 AD) gave an objection to the argument, although it would be toward ontological arguments in general, rather than at Anselm specifically.
Hildegard of Bingen, 1098 AD
Known as “The Sibyl of the Rhine”, she was one of the most impactful composer, philosopher, mystic, visionary, and a medical writer of the Middle Ages. She is revered as an early example of a feminist thinker. Scivias is the name of her illustrated work describing 26 religious visions she experienced. She is one of the best-known composers of sacred monophony, as well as the most recorded in modern history. She has been considered by scholars to be the founder of scientific natural history in Germany. She did not accept the inferior status of women in her era, and rejected male authority both in the ecclesiastical matters and in the music composition.

Héloïse, 1101 AD
Writer, philosopher of love and friendship, and the French nun, Héloïse, was one of the pioneers of the feminist thought. She is famous for her love story with Peter Abelard (who became her colleague, collaborator and husband), and the exerting critical intellectual influence upon his work and posing many challenging questions to him such as those in the Problemata Heloissae. The Problemata Heloissae (Héloïse’s Problems) is a letter from Héloïse to Abélard containing 42 questions about difficult passages in scripture, interspersed with Abelard’s answers to the questions.

Ibn Rushd (Averroes), 1126 AD
He combined Greek and Islamic thoughts. His philosophical works include numerous commentaries on Aristotle, for which he was known in the Western world as The Commentator and Father of Rationalism. Averroes was a strong proponent of Aristotelianism; he attempted to restore what he considered the original teachings of Aristotle and opposed the Neoplatonist tendencies of earlier Muslim thinkers, such as Al-Farabi and Avicenna. He proposed the “unity of the intellect” philosophical theory which asserted that all humans share the same intellect. He believed that not only religion and philosophy are complementary to each other, but the truths of philosophy and the Holy Book should also be consistent.

Zhu Xi, 1130 AD
He created an impactful philosophical system which is known as Neo-Confucianism. Neo-Confucianism slowly stopped the influence of Buddhism (which was considered foreign in China). The core of Zhu Xi’s philosophy is the relation between these two concepts: “Li” (meaning rational principle, law, or organisational rights), and “Chi” (aka Qi, meaning vital energy, material energy, or simply energy3). Li is not possible without Chi, and vice versa.

As an example, for a “human”, Chi is what the human is made of and keeps them healthy, while Li is both the physical and moral principles, e.g. having two hands, having two eyes, showing wisdom, practicing rituals, etc.

Moses Maimonides, 1135 AD
Maimonides was the physician, the lawyer, and the philosopher who first adapted Aristotle’s teachings to Jewish theology in his masterpiece, “The Guide For The Perplexed”. He believed that God’s nature will always remain unknown because it is beyond human understanding. He also believed that the meaning of the Torah (Hebrew Bible) should not be taken literally, and wherever it contradicts wisdom, we should try to interpret it (which happened to be very controversial among the Jewish scientists of the time).

Albertus Magnus, 1200 AD
Known as the “Doctor Universalis” because of the vast of his knowledge. He combined Aristotle’s thoughts with Christian teachings. He wrote about different topics, most notably the systematic study of minerals. His “De Mineralibus” is a five-volume book that became a benchmark text in mining, mineralogy, chemistry, and metallurgy. He also Discovered of the element Arsenic. As the teacher of Thomas Aquinas, he had important impacts in philosophy.

Thomas Aquinas, 1225 AD
He was an Italian Dominican friar and priest, and known as the most influential thinker of the Middle Ages. He is the author of “Summa Theologica”, in which he not only written a detailed description of Aristotle’s thoughts, but also expanded them and adopted them to Catholic ideas (in other words, made a mixture of science and faith). He believed that mocking the judgment of reason is mocking the judgment of God, and there is no conflict between philosophy and reason with church beliefs.

William of Ockham, 1285 AD
He believed that God can not be known directly, and God will always be incomprehensible to mankind. Therefore, in contrary to Thomas Aquinas’s belief, he did not accept the possibility of knowing the existence of God with mere reason, and believed that faith is necessary for this. Although he remained faithful to Catholicism, he gave way to agnosticism (the view or belief that the existence of God, of the divine or the supernatural is unknown or unknowable).

Adi Shankara
Al-Ghazali
Marsilio Ficino