 If the purpose and benefit of logic is to lead from what is known to what is unknown, for example from premises to conclusion in a valid argument whose premises are asserted, Avicenna’s account of the subject (mawḍūʿ) of logic is inextricably tied with a fundamental distinction in Arabic logic, which can be traced back at least to al-Fārābī, between the two main ways in which knowledge is available to the human mind: conception (taṣawwur) and assertion (taṣdīq).