Why should it be thought ... - The force of this question will be better seen by an exclamation point after why τί ti. “What! is it to be thought a thing incredible?” etc. It intimates surprise that it should be thought incredible, or implies that no reason could be given why such a doctrine should be unworthy of belief.
A thing incredible - A doctrine which cannot be credited or believed. Why should it be regarded as absurd?
With you - This is in the plural number, and it is evident that Paul here addressed, not Agrippa alone, but those who sat with him. There is no evidence that Agrippa doubled that the dead could be raised, but Festus, and those who were with him, probably did, and Paul, in the ardor of his speech, turned and addressed the entire assembly. It is very evident that we have only an outline of this argument, and there is every reason to suppose that Paul would dwell on each part of the subject at greater length than is here recorded.
That God should raise the dead - Why should it be regarded as absurd that God - who has all power, who is the creator of all, who is the author of the human frame should again restore man to life and continue his future existence? The resurrection is no more incredible than the original creation of the body, and it is attended with no greater difficulties. And as the perfections of God will be illustrated by his raising up the dead; as the future state is necessary to the purposes of justice in vindicating the just and punishing the unjust, and as God is a righteous moral governor, it should not be regarded as an absurdity that he will raise up those who have died, and bring them to judgment.