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Collect: O God to whom alone is known the mysterious workings of thy grace, grant me not to be presumptuous in thy sight, but give me lowliness and humility of heart, through Christ our Lord. Amen.
Summary
In the Sed Contra, Thomas cites an authority, i.e., Ecclesiasticus, in proof of his conclusion.
In the Respondeo, St. Thomas begins by distinguishing the three ways in which something may be known. First, a thing may be known by revelation from God. Obviously, in this way, God can communicate that we are in a state of grace.
Second, we may know something with absolute certainty (without prudent fear of error) from a process of reasoning. Thus, we conclude from our composite nature that we are mortal. In this way, we cannot know if we are in a state of grace, for, in order to know something in this way, we have to have a knowledge of those universal principles we reason from. Now, in the case of the working of grace, this is above and beyond nature, i.e., it is supernatural. Thus, we cannot conclude with such certainty that we are in a state of grace.