We attempt to grasp the mathematics behind the planetary theories of the Syrian astronomer Ibn al-Šāṭir (1304–1375) in his treatise Nihāyat al-Sūl. Following the astronomers of the Marāgha school, by composing circular movements with constant angular velocity, Ibn al-Šāṭir attains two goals. He eliminates the need of excentrics and equant points in astronomy; but he also describes longitudes and latitudes with a unique method, with no more orbs than what is strictly necessary for the longitudes. A better understanding of rotation as a spatial transformation enables this ultimate economy of thought. In our commentary, we take Venus as an example offering an interesting problem about the latitudes. This is an opportunity to give a critical edition of the chapter of the Nihāyat al-Sūl dedicated to the latitudes of Mercury and Venus.

This article explores the reception of Avicenna's theories of motion in the sixth/twelfth century. Avicenna had devised innovative ways of understanding motion in response to various challenges and conditions that the preceding philosophical tradition and his own internal critique had posed. Motion for him was either the state of being between two termini or the traversal of an interval, where the former of these was the extramentally real type and the latter a product of the imagination. In the sixth/twelfth century, the implicit critique of some leading scholars led to the adoption of the thesis in some circles that motion by traversal is extramentally real. This position was accepted as viable both by those who endorsed the atomic and the continuous theory of bodies.

Man's individual responsibility is a very central notion in Muslim theology. Rational foundations for moral responsibility presuppose, however, that man has in some way control over his actions. It was therefore of central concern to theologians to formulate theories of action that were coherent enough to account for human self-determination. This article examines al-Bāqillānī's reflections on human acts and attempts to contextualise his thought within the discussions of his time. I will briefly review the Muʿtazilites’ theory of freedom of action, against which the Ašʿarite school developed its own position. I will then outline the fundamentals of the opposing standpoint adopted by Abū al-Ḥasan al-Ašʿarī, who proposed to base human self-determination on voluntariness. Finally, I will discuss how al-Bāqillānī drew on and further developed al-Ašʿarī's ideas. Based on the extant volumes of al-Bāqillānī's Hidāyat al-mustaršidīn, I argue that he attempts to coherently organise the school's understanding of the famous theory of “acquisition” (kasb) by affirming two fundamental principles: a) that human acts are created by God and b) that there is nevertheless a real correlation between man and his “acquired” acts.

In this paper, I propose to expose the logical structure al-Bāqillānī's argument for the existence of God and argue that it presents a distinctive type of argument that cannot be classified under the classical types of ontological, cosmological, and design arguments. The peculiarity of al-Bāqillānī's argument is related to the concept of God it presupposes. Developing Herbert Davidson's insights regarding this argument and criticizing Majid Fakhry's interpretation of it, I aim to clarify this concept of God by the concept of agency. In a nutshell, I argue that al-Bāqillānī presents a distinctive type of argument for the existence of God, which I propose calling the “cosmological argument from agency.” I consider it cosmological because it is an inference from the universe to the existence of God. Nonetheless, it is different from the classical versions of the cosmological argument for that the concept of agency and the idea of a personal deity play a central role in this argument.

Is it possible to invent a science that sets the rules for an ethical, logical and effective debate? Shams al-Dīn al-Samarqandī (died in the first half of the 14th century), a logician and Ḥanafī jurist thought it possible. He undertook the task of developing a general theory of scientific discussion that had a tremendous success and impact on Muslim scholarship. Ādāb al-baḥth wa-al-munāẓara, as he called it, is a set of ethical and logical principles, taken from Aristotelian logic and Islamic law. His major treatise Risālat Ādāb al-baḥth, initiated a new discipline in which dozens of treatises, commentaries and glosses were written. In my contribution, I will shed light on this neglected science, describe its structure, expose its functions and highlight its significance for the development of debates and intellectual dialogues in the later medieval Islam.

Professor Steven Harvey has honored us with a 28-page critique of our 2012 paper, “Avicenna among medieval Jews.” In our opinion, his text is wanting in both form and substance.