Final Article

Article 16. Whether prudence can be lost through forgetfulness?

The Philosopher says (Ethic. vi, 5) that "forgetfulness is possible to art but not to prudence."

I answer that, Forgetfulness regards knowledge only, wherefore one can forget art and science, so as to lose them altogether, because they belong to the reason. But prudence consists not in knowledge alone, but also in an act of the appetite, because as stated above (Article 8), its principal act is one of command, whereby a man applies the knowledge he has, to the purpose of appetition and operation. Hence prudence is not taken away directly by forgetfulness, but rather is corrupted by the passions. For the Philosopher says (Ethic. vi, 5) that "pleasure and sorrow pervert the estimate of prudence": wherefore it is written (Daniel 13:56): "Beauty hath deceived thee, and lust hath subverted thy heart," and (Exodus 23:8): "Neither shalt thou take bribes which blind even the prudent [Douay: 'wise']."

Nevertheless forgetfulness may hinder prudence, in so far as the latter's command depends on knowledge which may be forgotten.

http://www.newadvent.org/summa/3047.htm#article16