Truth Conditions of Hypothetical Propositions According to Fakhr al-Dīn al-Rāzī
Fatma KaraismailThis article examines the truth conditions of conditional (muttaṣil) and disjunctive conditional (munfaṣil) propositions in Fakhr al-Dīn al-Rāzī’s (d. 606/1210) logic system and whether these propositions can be classified under truth functional propositional logic. Accordingly, the work is structured in two main sections. The subject is discussed in the first section in the context of implicative (luzūmī) and coincidental (ittifāqī) conditional propositions, and in the second section within the framework of three types of disjunctive conditional propositions. This study concludes that the truth values of implicative conditional propositions depend not only on the truth values of their components but also on whether they contain the implication relation. Similarly, the truth values of disjunctive conditional propositions are based on whether they include the conflict (ʿinād) relation, as well as on the truth values of their components. As a result, it has been established that the implicative conditional and disjunctive conditional propositions in al-Rāzī’s system are not truth functional and these propositions do not overlap in meaning with truth functional compound propositions in propositional logic. In contrast, coincidental conditional propositions are considered truth functional due to the absence of any implication or conflict relationship between their components.
Fahreddin er-Râzî’ye Göre Şartlı Önermelerde Doğruluk
Fatma KaraismailBu makale, Fahreddin er-Râzî’nin (ö. 606/1210) mantık sisteminde yer alan bitişik ve ayrık şartlı önermelerin doğruluk kriterlerinin ne olduğu ve bu önermelerin doğruluk işlevli (truth functional) olup olmadıkları sorularını ele almaktadır. Bu doğrultuda çalışma iki ana bölüm olarak kurgulanmıştır. Birinci bölümde mesele, lüzûmî ve rastlantısal (ittifâkî) bitişik şartlı önermeler, ikinci bölümde ise ayrık şartlı önermelerin üç türü bağlamında tartışılmıştır. Bu tartışma neticesinde lüzûmî bitişik şartlı önermelerin doğruluğunun, bileşenlerinin doğruluk değerlerinin yanı sıra bu önermelerin içermeleri gereken lüzûm ilişkisine sahip olmalarına; ayrık şartlı önermelerin doğruluğunun ise bileşenlerinin doğruluk değerlerinin yanı sıra ifade etmeleri beklenen ayrıklık ilişkisini ifade ediyor olmalarına bağlı olduğu sonucuna varılmıştır. Bunun sonucu olarak, Râzî’nin sistemindeki lüzûmî bitişik şartlı ve ayrık şartlı önermelerin doğruluk işlevli olmadığı ve bu önermelerin, önermeler mantığındaki doğruluk işlevli bileşik önermelerle anlam açısından örtüşmediği belirlenmiştir. Rastlantısal bitişik şartlı önermeler ise bileşenleri arasında gerektirme veya ayrıklık ilişkisi bulunmaması nedeniyle doğruluk işlevli olarak değerlendirilmiştir.
This article analyzes the truth conditions of hypothetical propositions (qaḍiyya sharṭiyya) in Fakhr al-Dīn al-Rāzī’s logic system and whether these propositions are truth functional or not. Truth functional compound propositions contain truth functional logical connectives and their truth values are determined based on the truth values of their components. On the other hand, non-truth-functional compound propositions are propositions whose truth values are not determined according to the truth values of their components. al-Rāzī’s theory of hypothetical propositions falls under propositional logic, as it examines new propositions formed by combining others through logical connectives and analyzes the relations between their components. However, does this theory also belong to truth functional propositional logic, which is the most comprehensive branch of propositional logic? This question, which points to the purpose of the article, is addressed in the context of conditional propositions (qaḍiyya sharṭiyya muttasila) in the first section and disjunctive conditional propositions (qaḍiyya sharṭiyya munfaṣila) in the second section. In these two chapters, first, the types of conditional and disjunctive conditional propositions according to al-Rāzī are briefly explained, followed by al-Rāzī’s explanations of the truth conditions of each of these propositions. In the first section, the problem is examined in two sub-sections for implicative (luzūmiyya) and coincidental (ittifāqiyya) conditional propositions.
According to al-Rāzī, implicative conditional propositions may be either true or false when the truth values of their antecedents and consequents are true and true, false and false, or false and true, respectively. The fact that the truth value of implicative conditional propositions may also be false when their components have these truth values distinguishes implicative conditional propositions from material conditionals. This is because material conditionals are necessarily true when the components have these truth values. The reason of this difference between implicative conditional propositions and material conditionals is the relation of implication (luzūm) that must exist between the antecedent and consequent in implicative conditional propositions. In other words, according to al-Rāzī, implicative conditional propositions mean that the antecedent necessarily entails its consequent and as a result, an implicative conditional proposition cannot be true if the antecedent does not necessarily entail the consequent even if they are both true. According to al-Rāzī coincidental conditional propositions are truth functional because they do not carry the meaning of implication. However, they also do not have the meaning of material implication, as a coincidental conditional proposition with a false antecedent and a false consequent is false.
al-Rāzī categorizes disjunctive conditionals into three types: (i) Real disjunctive conditionals (ḥaqīqiyya): According to al-Rāzī, real disjunctive conditionals are propositions in which one component is contradiction of the other. Since it is impossible for two mutually contradictory propositions, such as p and not p, to be true at the same time, one of the components of real disjunctive conditional propositions must be true and the other false. (ii) Mani‘at al-jam‘ disjunctive conditionals are propositions in which one of the components has a narrower scope than the contradiction of the other. (iii) Mani‘at al-ḥuluv disjunctive conditionals are propositions in which one component has a broader scope than the contradiction of the other. In mani‘at al-jam‘ disjunctive conditionals, all components can be false but cannot all be true. Conversely, in mani‘at al-ḥuluv disjunctive conditionals, all components can be true but cannot all be false. In conclusion, according to al-Rāzī, the meanings of disjunctive conditional propositions are determined by the law of non-contradiction. Therefore, the truth values of the components of disjunctive conditional propositions are not the only condition for determining the truth values of these propositions. When determining the truth value of these propositions, we consider not only the truth values of the components but also whether the conflict (ʿinād) relationship mentioned by al-Rāzī exists between the components. This shows that the types of disjunctive conditional propositions are also not truth functional.