Some verbs are becoming more defective as time goes on; for example, although "might" is etymologically the past tense (preterite) of "may", it is no longer generally used as such (*"he might not pass" for "he was forbidden to pass"). Similarly, "should" is no longer used as the past of "shall", but with a separate meaning indicating possibility or moral obligation. (However, the use of the preterite form "should" as a subjunctive form continues, as in "If I should go there tomorrow, ...", which contrasts with the indicative form "I shall go there tomorrow".) The defective verb "ought" was etymologically the past tense of "owe" ("the affection he ought his children"), but it has since split off, leaving "owe" as a non-defective verb with its original sense and a regular past tense ("owed").