  Ibn Gabirol also authored (in Arabic) On the Improvement of the Moral Qualities (islâh al-’akhlâq in the Arabic, or tîkkûn mîdôt ha-nefesh, the Hebrew title of the translation by Judah Ibn Tibbon) a blend of physiological and philosophical insights on the nature of the human soul. We also have evidence in other medieval Jewish authors of what might be part of an allegorical commentary on the Bible by Ibn Gabirol (as found in Abraham ibn Ezra's commentary on the Bible; see Friedlaender 1877, p. 40; Kaufmann 1899, p. 63ff.; for English see Sirat 1985, p. 79), and it is debated whether he might also be the author of Choice of Pearls (mukhtâr al-jawâhir, lit. Choice (or: Selection) of Jewels; or Mivhar ha-Penînîm, Choice of Pearls, in its Hebrew  translation),[9] a collection of maxims aimed at cultivating a virtuous soul. It might be further noted that there are medieval lists by later thinkers enumerating a total 21 treatises by Ibn Gabirol (see Loewe 1989, pp. 24–5) including an entire [non-extant] treatise on Divine Will to which Ibn Gabirol himself alludes in his Fons Vitae. All this, of course, in addition to his having authored a vast corpus of Hebrew poetry, including a number of lengthy philosophical poems (see section 7).