# When we use "could" to say there is a possibility, do we change the tense in the subordinate clause?

"Could" can be used to say something is a possibility, which has a similar meaning to that of "might." The tense in the subordinate clause after "might" doesn't change. But when we use "could" in this sense, do we change the tense in the subordinate clause?

Example 1

The tense in the subordinate clause remains unchanged.

He has been doing lots of math recently. He might think that he will get good grades on the math exam tomorrow.

Example 2

What tense do we use when we use could here?

He has been doing lots of math recently. He could think that he will/would get good grades on the math exam tomorrow.

• will in both cases. But bear this in mind: He could/might think that he would get good grades if he studied harder. Maybe this should be an answer... Oct 3, 2021 at 14:25
• Perhaps you're being misled by could in the second example, which can be used for both current and future possibilities. Compare He could be dead (now) and He could die (in the future). In your example, it seems to me that if we interpret he could think [something] as referring to what he might think now, the relevant thought is that he will do well (if he studies hard). But if we interpret could as referring to what he might think tomorrow (which is hypothetical irrealis "not present"), he would do well if he studied hard. Oct 3, 2021 at 16:28