Gelenbevî (İsmail)

Mathematician, astronomy and logic scholar (B. Kırkağaç/Manisa, 1730 - D. Mora/Yenişehir, 1791). Although his real name was İsmâil; he was generally known as Gelenbevî. He sometimes used pseudonym “Şeyhzâde” in some works. Belonging to a well-known family, his grandfather Mahmud Efendi and and his father Mustafa Efendi was scholars and both them worked as teacher and mufti. Due to the loss of his father at his young age, he couldn’t take an adequate education till the age of thirteen and fourteen, then he moved to Istanbul to study at Fatih Madrasah where he learned Arabic and took lessons on narrative sciences from one of the famous professors of the time, Yasincizâde Osman Efendi and took courses on mental sciences from Müftîzâde Mehmed Emin Efendi who was known as “walking library”. After completing his education at the madrasah in 1763, he held various positions of unknown details. The resources, in this period, states that he spent his time by examining the works on mathematics and logic and by writing in his house which was at the Zeyrek district of Istanbul.

Gelenbevi attended the sereneness classes as a guest lecturer in 1783. He later worked as the mathematics teacher in prominent education institutions such as; Mühendishâne-i Bahrî-i Hümâyun (T.N. Engineering School) and İstihkâm Mektebi (T.N. Military Engineering School) that were established following the reform movements during the reign of Abdulhamid I.

Gelenbevi became famous for his contribution to the research of a French engineer who came to Istanbul in 1787 to present his research to Bâbıâli (the Government). The Ottoman scholars didn’t understand how to use the logarithmic tables of the French engineer. Thereupon, Gelenbevi wrote a commentary to explain the usage of the tables in Turkish named “Şerh-i Cedâvili'l-ensâb” which is also known as “A Commentary on Logarithm” and through this work, he proved his genius.

  According to the historical sources, his achievement was appreciated during a meeting including the French engineer by the Chief of the External Affairs Mehmed Râşid Efendi’s gift for him a sable for divan to celebrate his success. It is understood that Gelenbevi took the advantage of the Turkish translation of the tables as Tuhfe-i Behîc-i Rassinî Tercüme-i Zîc-i Kassinî by Kalfâzâde İsmâil Çınârî Efendi upon the order of Mustafa III. while writing his commentary.

  Following an event that occurred in the presence of Selim III.; the people’s attention was drawn on him again. During the ceremony of holiday greetings that was held in Kâğıthane, the Sultan, upset by the failure of the artilleries to hit their targets, ordered to find an expert to compute the direction calculations correctly. Gelenbevi, appearing before the Sultan, corrected the angle errors in the cannons through detailed mathematical calculations. So, the artilleries hit the targets. Because of this success, Selim III. rewarded him by various gifts.

  In 1790, Gelenbevî İsmâil Efendi was appointed to the Yenişehir in Mora district (Yenişehr-i Fenâr, Larissâ) as kadi (Muslim judge) and during his duty, he died in Yenisehir. According to a rumor, his body was buried in a cemetery of Yenisehir’s Bayrakli Mosque. However, Ebül'ulâ Mardin claimed that he was buried in the mausoleum near to the Kostern Bridge in the Thessalia district of Greece.

  Gelenbevi İsmâil Efendi was one of the most important Ottoman scholars who had the right to comment on almost all the positive sciences and on the oral sciences and he is also an important scholar for expressing the scientific understanding of the Ottoman world. Although he lived on the declining period of the Ottoman State, he was able to apply scientific theory to practical problems and made his scientific capability accepted among the European scholars. And he carried his reputation to the four corners of the earth. He was also one of the last representatives of the classical Islamic algebra in Ottoman World. There is a high school in Fatih, Istanbul, (Gelenbevî Lisesi)  named after him.

  WORKS:

  RHETORIC and GRAMMAR: Risale ti 'ilmi'i-me'ânî. Resâ'ilü'I-imtihân, Risale fî 'ilmi'I-beyân, Resâ'i-lü'l-imtihan,  Risâletü'l-faşl ve'l-vaşl, Risâle-i Tağlib (As 48^th article in Resâ'ilü'l-imtihân), Risâle fî şerhi tarîfisıdki'l - haber ve kezibih, Risâle fi beyânı ismi'l-ma'nâ ve ismi'l-ayn, Risâle fî duhûli'l-bâ ale'l-makşûri uleyh (As the 11^th article in Resâ'ilü'l-imtihân).

  LOGIC-PHILOSOPHY-DISCUSSION: el-Burhan / fî ilmi'l mantık ve fenni'l-mîzân (This manuscript was written by the author especially for a hâşi under the name of Hâsiyetü'I-Burhân), Şerh-i 'Îsâgücî / Gelenbevî alâ İsâğocî (A commentary of famous Îsâğucî booklet on the issues of classical logic), Risâletü'l-kıyâs, Risâletü'l-imkân (aka. Mittâhu bâbi'l-müveccehât), Hârişiye alâ Hâşiyeti'l-Lâri alâ Şerhi Hidâyeti'l-hikme, Hâşiye alâ Tehzîbi'l- mantık ve'I-kelâm, Risâle fi'i-vâsıta (13^th booklet in Resâ'ilü'l-imtihân), Risale fî ma'ne't-taksîm, Risâletü'l-âdâb / Risâle fî ilmi'l âdâb (aka. Adâb Risalesi or Ge-lenbevi ale'l-âdâb), Ta'likât alâ Hâşiyeti Mîr alâ Şerhi'l-Âdâb.

  KALAM: Hâşiye alâ Şerhi'l-Celâl, Ta'lîkat alâ Hâşiyeti's-Siyâl-kûtî el-'Aka idü'l-Adudiyye, Risâle fî tahkîki mezâhibi ehli's-sünne fî usâti'l-müminîn, Risâle tete'allak bi-kavlihî Te'âIâ: Ve lev alima'llâhü fîhim hayran Ie-esme'ahüm, Risâle fî tahkiki vahdeti']-vücûd (A criticism of the term “wahdat al-wujud” (T.N. Unity of Existence) through the views of different philosophers), Risale fi't-tekaddüm, Risâle tete'allak bi-Kıdemil-'âlem ve (49^th article in Resâ'ilü'l-imtihân), Risâle tebhasü an mâhiyyâti'l-mümkinât ve'l-mümteni'ât, Risâle fî ilmi'l-kadîm ve te'allukıh, Risâle fî ilmi'llâhi Te'âlâ bi'l-ma'dû- mât alâ mezhebi'l-mütekellimîn, Risâle fi'I-vû-cûdi'z-zihnî (on an object’s existence by discussing  its relation to the inner world and to the material world).

  MATHEMATICS-ASTRONOMY: Hisâbü'l - küsûr / Küsûrât-ı hisâb, Risâle-i Adlâ-i Müsellesât (Three volume books on geometry), Şerh-i Cedâvili'l ensâb (It is also known as the Commentary on Logarithmic table), Usûl-î Cedâvil-i Ensâb-ı Sittînî (A small booklet on the logaritma cetvelleri), Risâle alâ rub'i'l-mukantarât (On astronomy. The work is also mentioned as Kitâbü'l-Merâsıd, Risâletü'l-ceyyib ve'l-mukantara and Amel bi'r-rub i'l-müceyyeb. It has a prominent place regarding the history of mathematics in Muslim world), Risâle fi sütû-hi'l-münharifât (A small booklet on the accounting of the height pivots in gnomons), Deka iku'l-beyân fi kıbleti'l-buldân (aka. Risâletü'l-kıble. A booklet on the determination of the qibla for different settlements).

REFERENCE: İbrahim Alaeddin Gövsa / “Gelenbevî İsmail Efendi” (Türk Meşhurları, 1946), Hilmi Ziya Ül­ken / Mantık Tarihi (1942), Kemal Zülfü Taneri / Türk Matematikçileri (s. 61 68, 1958), Abdülkuddûs Bingöl / Gelenbevî İsmail (1988), Abdurrahman Aygün / “Türk İrfan Semasının Şanlı Dâhisi ve Direği Gelenbeli İsmâil Efendi Merhum” (Diyanet İş­leri Başkanlığı Dergisi, 1961), İhsan Fazlıoğlu / “Cebir” (TDV İslam Ansiklopedisi, c.7, 199-200, 1993), İhsan Işık / Ünlü Bilim Adamları (Türkiye Ünlüleri Ansiklopedisi, C. 2, 2013) - Encyclopedia of Turkey’s Famous People (2013) - Resimli ve Metin Örnekli Türkiye Edebiyatçılar ve Kültür Adamları Ansiklopedisi (C. 12, 2017).