Read this: In early 12th-century al-Andalus, the Arabian philosopher, Ibn Tufail (Abubacer), wrote discussions on materialism in his philosophical novel, Hayy ibn Yaqdhan (Philosophus Autodidactus), while vaguely foreshadowing the idea of a historical materialism.

What book by Ibn Tufail did not discuss materialism? 
What is the answer? (If it cannot be answered, return "unanswerable")
unanswerable