These are statements containing "denial and affirmation" (al-nafy wa al-ithbat)...

These are statements containing "denial and affirmation" (al-nafy wa al-ithbat), "praise and reprobation" ( al-madh wa al-dhamm) as well as "wonder" (ta`ajjub), while "question" (istifham), "order and interdiction" ( al-'amr wa al-nahy), "regret" ( 'asaf ), "hope" ( tamanni) and "request" (mas'ala) are neither true nor false (al-Ash'ari, 1980, p. 444).

The Mu`tazila seem to have been little occupied with how true knowledge is reached, and this is perhaps due to the fact that they discussed truth in connection with the reliability of prophetic sayings - which is not an art to be taught.

The Mu"tazila had different opinions as to whether a proposition can be called true or false if its author was ignorant of the "actuality of affairs." (The question here is whether unintended deception can be called a lie, or whether a statement that incidentally happened to be exact can be called truth).

When the relevant "actuality of affairs" does not exist (for example, if the event has not yet occurred) or is unknown to a person, the verification procedure that compares a proposition to the "truth of things" cannot be executed - for objective and subjective reasons respectively - and such a proposition is to be regarded as neither true nor false. This argument, however, was not generally accepted by the Mu"tazila.

As for Aristotelian logic, it took root in medieval Islamic thought above all due to peripatetism. This school gave much more sophistication to what the Mutakallimun said about truth and the possible ways of acquiring it. Many elements of Aristotelian logic introduced by the Islamic peripatetics became indisputable patterns of reasoning for Islamic thinkers, and no school of medieval philosophy seriously challenged the syllogism as a paradigm for the preservation of truth in argumentation.

What was disputed was the sphere in which the syllogistic method is relevant. This method appears to have gained less favor among Islamic thinkers than it did among ancient or medieval Western thinkers, and in philosophy per se we find even among the peripatetics great reservations in this respect.

Elements of Aristotelian logic were rather well known to Islamic scholars from translations of Aristotle's works as well as from writings of his great commentators, among which must be mentioned in particular Porphyry's Eisagoge.