 These ideas—the series, its vertical pattern, the distinction between internal and external causes and a transcendent principle of the series—are also elaborated in the Kitāb al-Išārāt (see IV, 9–15; IV, 1–8 for its premises)— Remarks and Admonitions or Pointers—as the title of the work is known in English —, a work of extreme importance for the Eastern philosophical tradition. The Išārāt argument has been defined as a priori or ontological (Mayer 2001; cf. Marmura 1980). It originates from the general consideration of “every existent”: once examined in their essence (min ḥayṯu dāti-hi), or in isolation, without anything other than themselves, all existents either necessarily have or do not have existence in themselves: that which exists in itself is real or true (al-ḥaqq), it necessarily exists (al-wāǧib al-wuǧūd) and always subsists (al-qayyūm: an Islamic theological term); that which does not have existence in itself is always in need of a connection to something other, namely a condition (šarṭ) that will accompany it, both when it is conceived as existent and when conceived as non-existent. Thus, conceiving a causal chain means positing the existence of something that is prior and external to it. If the connection of the possible with something other than itself were continuously repeated, ad infinitum, each unit in the chain would be possible in itself, and the collection (ǧumla) that the units constitute would also, in itself, be unnecessary. In order to devise a collection of things, possible in themselves but existing, one must conceive of a collection rendered necessary by virtue of something external to it. The propensity to exist, which is necessity, is ascribed to the units of a collection, and hence to the collection itself, by something that, transcending it, is necessary in itself.