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  • From My NotebooksOn Tajriba/Nissayon (“Experience”): Texts in Hebrew, Judeo-Arabic, and Arabic
  • Y. Tzvi Langermann (bio)


A research project that I undertook some time ago, and which came to fruition in a paper entitled “Maimonides’ Repudiation of Astrology,” led me to investigate the concept of tajriba or “repeated experience.”1 In the medieval debate over astrology, tajriba is a key concept. Astrologers claim that the experience accumulated over the ages, in which certain stellar configurations are repeatedly synchronous with fairly specific terrestrial events (both natural and historical), establishes a sound connection between the two. This is the epistemological basis of the art of astrology, which makes predictions for the future on the basis of (what are claimed to be) repeated experiences of the past. The opponents of astrology, Maimonides among them, reject this claim. Maimonides, as a good Aristotelian, demands of a true science that it identify causes and prove formally that they are causes. Tajriba cannot do this; hence an art such as astrology that relies solely upon tajriba is not a true science. [End Page 147]

Not that Maimonides and those who agree with him on this point totally deny tajriba as a possible source of knowledge: medical practice, in particular, must employ remedies whose efficacy has been ascertained repeatedly, even if one cannot explain why they work. Indeed, in his Guide, Maimonides ratifies the rabbinic permission for some obviously pagan practices—the Talmud calls them “the ways of the Amorites” — because their reputed therapeutic effect has been validated by experience:

You must not consider as a difficulty certain things that they have permitted, as for instance the nail of one who is crucified and a fox’s tooth.2 For in those times these things were considered to derive from experience (tajriba) and accordingly pertained to medicine and entered into the same class as the hanging of a peony upon an epileptic3 and the giving of a dog’s excrements in cases of the swelling of the throat and fumigation with vinegar and marcasite in cases of hard swellings of the tendons. For it is allowed to use all remedies similar to these that experience has shown to be valid even if reasoning (qiyās) does not require them. For they pertain to medicine and their efficacy may be ranged together with the purgative action of aperient medicines.4

Three points may be drawn from Maimonides in connection with tajriba and its place in medieval scientific discourse. (1) Tajriba is an epistemological foundation of applied arts or sciences.5 (2) In the exact sciences, tajriba plays no role at all. (3) Medicine straddles the middle ground: it aims to be a science like the other sciences, but it cannot avoid including in its pharmacopoeia remedies that have no rational justification but whose efficacy has been demonstrated by tajriba.6

The claim that tajriba is irrelevant to the exact sciences can be justified from the writings of Maimonides only by an argument ex silentio: [End Page 148] nowhere in his discussions of astronomy—for example, in the chapter of the Guide devoted to astronomy (II, 24)—does the term occur. More generally, I note that tajriba has no role at all in the interplay of astronomical theory and observation, an important theme in some of the best medieval science, and studied by eminent scholars such as Bernard R. Goldstein and George Saliba.7

This key observation was made in fact in a paper published some time ago by my late mentor, A. I. Sabra, who noted with some surprise [End Page 149] that Ibn al-Haytham does not use tajriba to describe his optical experiments, even though he does use istiqrāʾ, the standard Aristotelian term for induction.8 Instead, the optical and astronomical literature speaks of iʿtibār. Another term that we shall encounter in some of the Judeo-Arabic texts displayed in the second section of this paper, imtiḥān, meaning “test,” is also found in the astronomical texts cited by Sabra.9 In fact, Sabra found that the earlier translator of Ptolemy’s Almagest, al-Ḥajjāj, did use tajriba to render the Greek peira, but that Isḥāq bin Ḥunayn...


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