These great signs will be so spectacular that “there should be no cause for unbelief.” This situation is unusual; agency usually requires that there be the free option of belief. Does this situation violate agency?
In this case, it creates a terrible agency. Believers will have their belief confirmed. But verse 29 suggests that there will still be unbelievers. How can they still refuse to believe? I hypothesize that, because the events are associated with natural phenomena, unbelievers will ascribe those signs to natural causes. Their unbelief in the face of such a powerful sign will “bring upon themselves their own condemnation.” This is a terrible agency because it is a winnowing mechanism. It will confirm and save those who believe but condemn and destroy those who do not.