Aaron ben Joseph of Constantinople (c. 1260 – c. 1320) (not to be confused with his near-contemporary, Aaron ben Eliyahu of Nicomedia), was an eminent teacher, philosopher, physician, and liturgical poet in Constantinople, the capital of the Byzantine Empire.
Aaron ben Joseph was born in Sulchat, Crimea. He took a prominent part in the regeneration of Karaism by the help of philosophical elements borrowed from Rabbanite literature. When only nineteen years of age he had mastered the theological knowledge of his time to such a degree that he was elected the spiritual head of the Karaite community of his native town, and in that capacity he engaged the Rabbanite teachers in a public dispute to determine the correct time for the new moon. He then journeyed through many lands and diligently studied the works of Abraham ibn Ezra, Maimonides, Nahmanides and Rashi. Being, as he said, eager to arrive at "the truth without bias and prejudice, and free from partisan spirit," he determined to accept the results of his investigation, even if they conflicted with Karaite teachings and traditions. In this spirit of fairness he wrote, in 1294, while following the profession of a physician in Constantinople, the work which established his fame and influence despite his Rabbanite proclivities. This work was the "Mibhar" (The Choice), a commentary on the Pentateuch, written in the terse, concise, and often obscure style and after the critical method of Ibn Ezra, and this became to the later generation of Karaite teachers a source of instruction in religious philosophy, in exegesis, and in practical theology, that is, the observance of the Torah.
Like ibn Ezra, he presents his theology not in systematic and coherent form, but in observations made throughout the book, in connection with the various portions of the Torah. Unlike ibn Ezra, however, he avoids references to hidden mysteries of the Biblical text, insisting always on its plain meaning or its possible figurative significance. For the latter he especially uses the commentary of Nahmanides, whose pupil he is erroneously said to have been. Like Judah Hadassi and Maimonides, he accentuates the spirituality of God; but, unlike these, he assumes certain attributes of God to be inseparable from His essence, but to be taken rather as human forms of speech. In connection with this he dwells especially on the will of God, by which the world was created, and by which the celestial bodies are moved and governed. Angels are to him intelligences emanating from the divine intellect, not created beings; and the existence of demons he rejects as an absurdity. God's saying, "Let us make man!" he explains as signifying the cooperation of the spiritual with the sensuous in the creation and evolution of man; and when God is described as giving names to things, the meaning is that He prompts man to do so. Still, he opposes that rationalism which dissolves miracles into natural occurrences. Prophecy he explains as a psychological, not a physical, process, manifested in different forms; either the inner eye or ear perceiving the object in a vision or dream, or, the truth being on a higher plane, communicated intuitively. Only Moses received the divine revelation directly and clearly without any mind-obscuring vision. Abraham's call to sacrifice his son he takes to be a mere vision. Aaron is very outspoken on the subject of man's free will, opposing emphatically the notion held by ibn Ezra and others, that human destiny or disposition is influenced by the planets. The expression, that God hardened the heart of Pharaoh, he so interprets as not to contravene the principle of free will.