Therefore negligence is opposed to prudence. I answer that, Negligence is directly opposed to solicitude. Now solicitude pertains to the reason, and rectitude of solicitude to prudence. Hence, on the other hand, negligence pertains to imprudence. Therefore negligence pertains to imprudence.
Omission regards the external act, for it consists in failing to perform an act which is due.
Hence it is opposed to justice, and is an effect of negligence, even as the execution of a just deed is the effect of right reason. Hence fear makes us avoid negligence, yet not as though negligence were directly opposed to fear, but because fear incites man to acts of reason. But wherever there is mortal sin, the love of God is done away with altogether. Therefore negligence is not a mortal sin. Further, a gloss on Ecclus.