Following in the footsteps of the Greek philosophers, Muslim philosophers consider knowledge to be the grasping of the immaterial forms, natures, essences or realities of things. They are agreed that the forms of things are either material (that exists in matter) or immaterial (existing in themselves). While the latter can be known as such, the former cannot be known unless first detached from their materiality. Once in the mind, the pure forms act as the pillars of knowledge. The mind constructs objects from these forms, and with these objects it makes judgments.
Thus Muslim philosophers, like Aristotle before them, divided knowledge in the human mind into conception (tasawwur), apprehension of an object with no judgment, and assent (tasdiq), apprehension of an object with a judgment, the latter being, according to them, a mental relation of correspondence between the concept and the object for which it stands. Conceptions are the main pillars of assent; without conception, one cannot have a judgment. In itself, conception is not subject to truth and falsity, but assent is.
However, it should be pointed out that tasdiq is a misleading term in Islamic philosophy. It is generally used in the sense of ‘accepting truth or falsity’, but also occasionally in the sense of ‘accepting truth’. One must keep in mind, however, that when assent is said to be a form of knowledge, the word is then used, not in the broad sense to mean true or false judgment, but in the narrow sense to mean true judgment. In Islamic philosophy, conceptions are in the main divided into the known and the unknown. The former are grasped by the mind actually, the latter potentially.
Known conceptions are either self-evident (that is, objects known to normal human minds with immediacy such as ‘being’, ‘thing’ and ‘necessary’) or acquired (that is, objects known through mediation, such as ‘triangle’). With the exception of the self-evident conceptions, conceptions are known or unknown relative to individual minds. Similarly, Muslim philosophers divided assent into the known and the unknown, and the known assent into the self-evident and the acquired. The self-evident assent is exemplified by ‘the whole is greater than the part’ and the acquired by ‘the world is composite’.
In Kitab at-tanbih ‘ala sabil as-sa’ada (The Book of Remarks Concerning the Path of Happiness), al-Farabi calls the self-evident objects: ‘the customary, primary, well-known knowledge, which one may deny with one’s tongue, but which one cannot deny with one’s mind since it is impossible to think their contrary’. Of the objects of conception and assent, only the unknown ones are subject to inquiry. By reducing the number of unknown objects one can increase knowledge and provide the chance for happiness. 2. Conceptualization and assent
While the close links between logic and linguistic studies emerge in the Islamic philosophers’ consideration of the subject matter of logic, the links between logic and epistemology come to the fore in the consideration of the divisions within logic and the order of the books within Aristotle’s Organon. All the principal Islamic Aristotelians organize their understanding of the divisions of logic around the epistemological couplet of tasawwur (conceptualization), and tasdiq (assent), which constitute for them the two states of knowledge that logic aims to produce in the intellect.
Conceptualization is the act of the mind by which it grasps singular (though not necessarily simple) essences or quiddities, such as the concept of ‘human being’. Assent, by contrast, is the act of the intellect whereby it makes a determinate judgment to which a truth-value can be assigned; in fact, conceptualization is defined in Islamic philosophy principally by contrast with assent. Thus, any act of knowledge that does not entail the assignment of a truth-value to the proposition that corresponds to it will be an act of conceptualization alone, not assent.
More specifically, the Islamic philosophers link assent to the affirmation or denial of the existence of the thing conceived, or to the judgment that it exists in a certain state, with certain properties. Thus, assent presupposes some prior act of conceptualization, although conceptualization does not presuppose assent. One of the purposes of including a consideration of the tasawwur-tasdiq dichotomy in introductory discussions of the purpose of logic is to provide an epistemological foundation for the two focal points of Aristotelian logic, the definition and the syllogism (see Logical form §1).
The purpose of the definition is identified as the production of an act of conceptualization, and the purpose of the syllogism is identified as causing assent to the truth of a proposition. However, since the definition and the syllogism are both considered in the Prior and Posterior Analytics and the works that come after them in the Organon, the study of the ways of producing conceptualization and assent presupposes as its foundation the study of single terms and propositions in the Categories and De interpretation.