ABSTRACT
This chapter attempts to distinguish between eight different forms of expressions with truth-values. It determines how they fare with respect to the rules of inference of the Square of Opposition and how they fare with respect to the subsidiary rule of conversion. The chapter considers how Avicenna views the results of this test, one might be able to determine how he views a logical model which formalizes expressions with truth-values. It tries to concentrate on Avicenna's treatment of necessary and contingent statements, and determines in particular the behaviour of these statements. The chapter addresses a philosophical problem that has drawn much attention throughout the subject's history. The classic distinction between assertoric and modal statements should be treated with caution in Avicenna's case: for him all statements as the authors shall see of whatever kind, and regardless of whether or not a modal operator is expressed, are modal.
