Thomas Aquinas

In his own words on 2 Maccabees

• 2 Maccabees 12:39-45

  Moreover, the dead live in the memory of the living: wherefore the intention of the living can be directed to them. Hence the suffrages of the living profit the dead in two ways even as they profit the living, both on account of the bond of charity and on account of the intention being directed to them. Nevertheless, we must not believe that the suffrages of the living profit them so as to change their state from unhappiness to happiness or "vice versa"; but they avail for the diminution of punishment or something of the kind that involves no change in the state of the dead.

  Question 71. The suffrages for the dead, Article 2