Averroes (d. 1198) explains why Scripture addresses its adherents in different ways in the Fasl al-Maqal, II.11-12, 15 (ed. Hourani, Leiden: 1959, emphasis mine):
.والسبب في ورود الشرع فيه الظاهر والباطن هو اختلاف فطر الناس و تباين قرائحهم في التصديق
And tasdiq, he clarifies there, is either burhani (demonstrative), jadali (dialectical), or khitabi (rhetorical).
al-Mubahathat 