There’s a particular distinction between fortisan and fortasse (both meaning ‘perhaps’) that isn’t intuitive.
- Fortisan regularly take a (Potential) subjunctive, except in those rare moments of poetry, where it takes the indicative.
- Fortasse usually takes the indicative, except in those rare moments of poetry, where it takes the subjunctive.
- Fortasse occasionally takes an infinitive, but only in Roman Comedy
- Perhaps you will ask what all this fuss is: forsitan quaerātis quī iste terror sit.
- Perhaps I have acted rashly: forsitan temerē fēcerim.
- Perhaps you will ask me what all this fuss is about: quaerēs fortasse, quī iste terror sit.
- Perhaps that was a mistake: fortasse errāvī.
Other ‘Perhaps’ Constructions:
- forsan, chiefly takes the indicative, though it takes both pretty evenly-handed.
- fors, rare to begin with, it takes either the indicative or the subjunctive
- forsit / for sit, occurs just once, in Horace, and takes the subjunctive
- fortassis, rare and takes the indicative
- fortasse an (note the switch) is rare and takes the subjunctive (whereas fortasse is usually with the indicative)
The Essential AG: 447a-b