Hi everybody, I've got a doubt about the use of tenses with modal verbs governed by a past tense. Should the modal verb be present or past in a sentence like the following, with the verb "think" in the past? Here are two possible solutions. 1. He wasn't sure, but thought the new plan against unemployment could work. 2. He wasn't sure, but thought the new plan against unemployment could have worked. Possible explanation 1. If it is possible to accept both, is it correct to say that the meaning of the first sentence refers to the future and that of the second remains anchored in the past? Possible explanation 2. If, instead, the second sentence is not acceptable, what grammatical principle is implied? (A principle analogous to that of the future in the past which requires the use of a present conditional for actions that occur in the future compared to the past? Or is an agreement similar to that necessary with reporting verbs in the past simple that require the simple conditional after them? In addition to 'would', can we reason by analogy with all other modal verbs and follow this general rule? ) I hope my question is clear enough. Thank you.