Ita crediderim, sed certus non sum.
A brief discussion ensued about my choice of tense. I wanted to express hesitation, and my gut feeling says that the perfect conjunctive is best for that. I was far from being sure, and I wanted the verb to reflect that. I would like to have more than my intuition behind this: What difference is there in tone between the present and perfect conjunctive when used in such a situation?