Abd al-Latif ibn Yusuf al-Baghdadi (13th century CE, 7th century AH)

The Book of the Two Pieces of Advice by Abd al-Latif, the son of Yusuf, to the General Public (Kitab al-Nasihatain min Abd al-Latif b. Yusuf ila l-nas kaffatan). Bursa: MS Hüseyin Çelebi 823, item number 5; medical section on fol. 62a-78a; philosophical section: fol. 78b-100b.

Title page(s)

Key passage(s)


“When the conditions [shurut] of the medical art are fully adhered to, then it never makes a mistake. The intelligent physician only errs occasionally, but gets things right a hundred times, as Galen said. Moreover, his mistake will be neither decisive nor great nor far from what is correct. One can compare him to an expert in archery who mostly hits the mark, and when he misses then it [i.e., his arrow] will not be far off, but it will rather land near [the target]. But in the event of the arrow falling entirely in the opposite direction, then [this is like] a physician committing an error.”


“I shall give you as an example the surface of the circle or a square root such as that of [the number] ten. Someone skilled in this art determines this [irrational number] as closely as possible, and will tolerate [only] the smallest part [of error], the difference of which is not apparent to sense-perception; however, it is not equivalent to a small difference for the intellect [that is, the error cannot be perceived by the eye, but by the intellect]. Such a solution is deemed to be correct, even if a certain tolerance is present in it, provided that it does not exceed a part [that is, an amount] which basically does not count. As long as the part which one tolerates [that is, the margin of error] is small, the solution is quite correct, and the person arriving at it is quite skilled. Therefore, artful conjecturing in medicine is similar. Yet what is different to this [small amount of error] is evidently an error, and those who commit it are not deemed to belong to those exercising the art [of medicine]. Likewise, if someone says that the square root of ten is three, he cannot be counted as an arithmetician, and his words cannot be accepted. This is also valid for those who are in the same situation, namely those who claim to master the art of medicine without [actually] being a physician.” [fol. 64a14–65a1]

Translation by Peter Joosse and Peter Pormann