Obligation and freedom to act – future and past

Modal Past Future
1a Must Cannot use must Use rule 2a Cannot use must Use rule 2a
2a Have to had to will have to
3a Need to Needed to will need to
4a Should Should have should
5a Ought to Ought to have ought to
6a be allowed to were allowed to will be allowed to
7a Can could Cannot use can Use rule 6a


Modal Past Future
1b Must not Cannot use must Use rule 6b Cannot use must Use rule 6b
2b Do not have to did not have to will not have to
3b Need not/ do not need to did not need to will not need to
4b Should not Should not have should not
5b Ought not to Ought not have ought not to
6b Not allowed to were not allowed to will not be allowed to
7b Cannot Could not Cannot use cannot Use rule 6b


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