How does the sequence of tenses work?

The sequence of tenses is used in purpose clauses, indirect commands, fear clauses and result clauses. It decides which form of the subjunctive should be used in the subordinate clause. There are two types of tenses in the sequence of tenses: Primary tense, and Historic tense. These tenses are all Primary tense and are followed by the present subjunctive: The present The futureThe future perfectThe perfect with "have"ImperativesThese tenses are all Historic tense and are followed by the imperfect subjunctive:The imperfect The perfect The pluperfectSO... if the introductory verb in the sentence is in the present tense, the verb in the subordinate clause will be a present subjunctive! eg feles ad Londinium it ut reginam videat = The cat goes to London to see the queen (purpose clause)