The concept of ‘‘certitude” (yaqīn) is central in Arabic discussions of the theory of demonstration advanced by Aristotle in the Posterior Analytics. In the Arabic tradition it is ‘‘certitude,” rather than ‘‘knowledge” (‘ilm=Greek epistēmē), that is usually identified as the end sought by demonstrations. Al-Fārābī himself devotes a short treatise, known as the Conditions of Certitude (šarā’iṭ al-yaqīn), to determining the criteria according to which a subject can claim to have absolute certitude of any proposition. In this article the author traces the roots of the concept of certitude to the Arabic translation of the Posterior Analytics. She then offers a close reading of the text of al-Fārābī's Conditions and its parallels in his Epitome of the Posterior Analytics (Kitāb al-Burhān). She argues that the identification of certitude as a cognitive state distinct from knowledge enabled al-Fārābī to introduce a number of interesting and sometimes problematic innovations into Arabic epistemology. Foremost amongst his positive innovations is the recognition that contingent as well as necessary propositions allow for an attenuated form of certitude, and the introduction of reliabilism into the justification of claims to certitude. But al-Fārābī is also one of the first philosophers to articulate explicitly the idea that certitude must include an element of ‘‘knowing that one knows,” a controversial principle that tends to undermine both al-Fārābī’s reliabilism and his efforts to loosen some of the strictures in traditional Aristotelian epistemology.

Avicenna's discussion of space is found in his comments on Aristotle's account of place. Aristotle identified four candidates for place: a body's matter, form, the occupied space, or the limits of the containing body, and opted for the last. Neoplatonic commentators argued contra Aristotle that a thing's place is the space it occupied. Space for these Neoplatonists is something possessing dimensions and distinct from any body that occupies it, even if never devoid of body. Avicenna argues that this Neoplatonic notion of space is untenable on the basis of three arguments. In general he maintains that bodies' impenetrability is explained by reference to dimensionality. Consequently, if it is dimensionality that explains impenetrability, and yet as the Neoplatonists hold space inherently possesses dimensions, material bodies could never interpenetrate space and so occupy it and thus bodies could never have a place. The conclusion is patently false. In additions Avicenna argues that the method used to arrive at the possibility of space is illicit, and so Neoplatonist cannot show that space is even possible. Thus, concludes Avicenna, Aristotle's initial account must be correct. The paper outlines the historical context of this debate and then treats Avicenna's arguments against space in detail.

The spirits (arwāḥ) found in Arabic alchemical texts, namely zi'baq, kibrīt, nūshādir and zarnīkh are identified with their modern counterparts, which are mercury, sulfur, ammonium chloride (carbonate) and arsenic (arsenous) sulfide, respectively. Jābir's conception of spirits has been shown to be related to his practice. The puzzling experiments of Jābir on ‘mineral and organic’ spirits are compared as far as possible with modern knowledge of chemistry. These comparisons lead to an understanding of Jābir's sequence of manipulations within the logic of his alchemy. In treatment of naturally occuring spirits, Jābir aimed at removing the combustibility of spirits and so improving their effect on fusible bodies. Jābir's notion of transmutation (iqlāb) of fusible bodies is shown to be a flexible term that is equivalent to purification (tanẓīf) or reformation (iṣlāḥ).

Islamic polities of the classical period recognized the importance of seaweeds in their daily life. Their men of science, craftsmen, and navigators used them for medicinal purposes, manufacturing, and navigation. The agar components were used in treating pathological conditions such jaundice, spleen, kidney and skin ailments, and malignancies. As food, we stress that our conclusions derive from Qur'ān-based commentaries and Muslim religious law that encouraged seafaring and exploiting the resources of the sea. Concerning navigation, sailors could identify coastal trunk routes, shallows, and various marine phenomena; shipwrights used agar compounds as a protective coating against the Greek Fire. Like their Greco-Roman counterparts, Muslim physicians, chemists, botanists, and professional sailors of this period were acquainted with numerous species of seaweeds and could appreciate the actual scientific importance of each type as well as the aquatic environment where these species lived and developed. Their scholarly literature consists of several generic Arabic and Arabicized terms to denote seaweeds and the terms variations appeared to be physical rather than linguistic.

This article returns to an old but not hitherto satisfactorily solved question, and aims at putting forward a new approach to the study of the sources and authorship of two contemporary treatises on agriculture: the Nabatean Agriculture (in Arabic al-Filāḥa al-nabaṭiyya) and the Geoponica. Each of them embodies a long tradition reaching from Antiquity to the 10th century in two different cultural provinces expressed in Greek / Latin and Arabic languages. But there is another common feature of these works. Both of them survived in a significant number of manuscripts, and constitute a kind of revision of previous compilations which drew their contents from more ancient treatises brought to light between the 3rd and 6th centuries AD, and to some extent could be qualified as the outcome of an effort for systematising the corpus of agronomical science. Texts and translations from Greek to Latin, from Greek to Syriac or to Arabic, and from Arabic to Armenian attest to this cultural intercommunication.

Constantine the African's significance as the first important translator of medical texts from Arabic into Latin is indisputable due to the fact that his work contributed decisively to the enlargement of medical knowledge in the Latin West. Among his considerable œuvre the translation of al-Maˇgūsī's Kitāb al-Malakī under its Latin title Pantegni, the first real medical compendium in Latin, holds a particularly important position because of its popularity. The Pantegni is divided into the two parts Theory and Practice with ten books each. Yet while the Theorica Pantegni corresponds basically to the Theory in the Kitāb al-Malakī, this is only partly the case for the Practica Pantegni. The content of the differing parts has been put together mainly from other medical texts. The identification of these other medical texts was the aim of some important researches while the last ten years (see especially the articles in Charles Burnett and Danielle Jacquart [eds.], Constantine the African and ‘Alī ibn ‘Abbās al-Maˇgūsī: The Pantegni and Related Texts [Leiden / New York / Cologne, 1994]). The aim of this article is to present the sources of the Pantegni, Practica’s third book and to give some indications on the person who made the compilation who – as it seems – wasn't Constantine the African himself.