Universal 303: ergative construction (non-past V imperfect) V. passive voice (non-past V imperfect) ⇒ ⇒ ergative construction (past V perfective) V. passive voice (past V perfective)
Universal 303: ergative construction (non-past V imperfect) V. passive voice (non-past V imperfect) ⇒ ⇒ ergative construction (past V perfective) V. passive voice (past V perfective)
Original
If a language has an ergative construction or a passive voice in non-past or imperfective tenses, then it also has them in past and perfective tenses.
Standardized
IF there are ergative or passive constructions in non-past or imperfective tenses, THEN there are ergative or passive constructions in past and perfective tenses.