Being and Time raises the problem of "authenticity," that is, the potentiality or otherwise for mortal "Dasein" to exist "fully" enough that it might actually understand being. Heidegger is clear throughout the book that nothing makes certain that "Dasein" is capable of this understanding. Finally, this question of the authenticity of individual "Dasein" cannot be separated from the "historicality" of "Dasein". On the one hand, "Dasein", as mortal, is "stretched along" between birth and death, and thrown into its world, that is, thrown into its "possibilities", possibilities which "Dasein" is charged with the task of assuming. On the other hand, "Dasein's" access to
Philosophy and literature narrative "Philosophus Autodidactus" as a response to al-Ghazali's "The Incoherence of the Philosophers", and then the 13th century Islamic theologian-philosopher Ibn al-Nafis also wrote a fictional narrative "Theologus Autodidactus" as a response to Abubacer's "Philosophus Autodidactus". The German philosopher Friedrich Nietzsche often articulated his ideas in literary modes, most notably in "Thus Spoke Zarathustra", a re-imagined account of the teachings of Zoroaster. Marquis de Sade and Ayn Rand wrote novels in which characters served as mouthpieces for philosophical positions, and act in accordance with them in the plot. George Santayana was also a philosopher who wrote novels and poetry; the