The presentation of conditional clauses in Latin involves but little difficulty until we come to those that are expressed by a verb in the present subjunctive. It is easy to understand that the past tenses of the subjunctive convey an unreal or imaginary supposition, one contrary to the facts of the case, while with a verb in the indicative we have an open supposition, in which there is no implication as to the facts: but what of the present subjunctive? How does si quid habeam differ from si quid habebo, if both suppositions have regard to future time?