Avicenna gave a number of accounts of modal propositions and syllogisms. Here, I follow a few points made in the one given in Pointers and Reminders, the cynosure of thirteenth-century logicians (though I also refer to Salvation which, like Pointers, is available in English translation). Avicenna's syllogistic includes propositions without explicit modalization (an absolute proposition, taken by Avicenna to contain an elided temporal modality “at least once”, so the a-proposition is understood as “every J is at least once B”, the e-proposition as “no J is always B”) both one- and two-sided, possibility propositions both one-sided (“every J is possibly B”) and two-sided, and necessity propositions (“every J is necessarily B”,  e-proposition “no J is possibly B”).