 The scheme of classification of disjunctive propositions is analogous to that of conditionals. Disjunctive statements consisting of two parts are quantified as a-, e-, i-, and o-propositions (where negative propositions express absence of conflict or incompatibility between the disjuncts at all (some) times and under all (some) circumstances) with sixteen permutations for each case depending on the quality and quantity of the parts (see  Appendix B). In this case, however, the situation is complicated by the fact that different types of disjunctions have different logical properties, with specific considerations applying to each type. Besides, in the schematic representations offered below, I prefer to retain the quantificational features of the disjuncts, as Avicenna seems to differentiate explicitly between real and unreal disjunctions in virtue, among other things, of their having affirmative or negative parts, another point that deserves more attention (for a preliminary analysis see Street 1995). In general, for Avicenna disjunctions and conditionals are not inter-definable without qualification.