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In the last three articles of this question, St. Thomas begins to apply the principles of the first three articles on the nature and scope of God's potentia in order to determine individual questions.
These individual questions, while interesting, do not require a full exposition, but only a short summary with parallel passages noted
Whether God can make the past not to have been?
cf., ST.II-II.Q152.A3.Rep3; Sent.I.D42.Q2.A2; SCG2.C25; QDePot.Q1.A3.Rep9; QV.Q2.A1; Eth.Bk6.L2
The first answer was one that was hotly debated in the medieval era. This is often connected with the question of whether God could make a woman who has had relations a virgin again.
The answer to this question is no. The reason for this is that the past can either be or not be. If it was, then to make it not be would be to make it both be and not be, which is a contradiction. If it is not, then it never was, for it isn't.
To apply it the virgin question, it would be to say both that, "X had sex" and "X did not have sex," which would be manifestly contradictory, just as if we were to say both that "Socrates is sitting" and "Socrates is not sitting. Since time is nothing to God, to make an assertion as past and make one as present makes no difference.
Thus, this falls outside of the scope of the "possible" as outlined above.
Respondeo: As was said above (Q. 7, A. 2), there does not fall under the scope of God’s omnipotence anything that implies a contradiction. Now that the past should not have been implies a contradiction. For as it implies a contradiction to say that Socrates is sitting, and is not sitting, so does it to say that he sat, and did not sit. But to say that he did sit is to say that it happened in the past. To say that he did not sit, is to say that it did not happen. Whence, that the past should not have been, does not come under the scope of divine power. This is what Augustine means when he says (Contra Faust. xxix, 5): Whosoever says, If God is almighty, let Him make what is done as if it were not done, does not see that this is to say: If God is almighty let Him effect that what is true, by the very fact that it is true, be false: and the Philosopher says (Ethic. vi, 2): Of this one thing alone is God deprived—namely, to make undone the things that have been done.