To Trace All Souls Day | Fr. Brian Van Hove, S.J. | Ignatius Insight
As Cardinal Joseph Ratzinger once said so well, one major difference between Protestants and Catholics is that Catholics pray for the dead:
"My view is that if Purgatory did not exist, we should have to invent it." Why?
"Because few things are as immediate, as human and as widespread—at all times and in all cultures—as prayer for one"s own departed dear ones." Calvin, the Reformer of Geneva, had a woman whipped because she was discovered praying at the grave of herson and hence was guilty, according to Calvin, of superstition". "In theory, the Reformation refuses to accept Purgatory, and consequently it also rejects prayer for the departed. In fact German Lutherans at least have returned to it in practice and have found considerable theological justification for it. Praying for one's departed loved ones is a far too immediate urge to be suppressed; it is a most beautiful manifestation of solidarity, love and assistance, reaching beyond the barrier of death. The happiness or unhappiness of a person dear to me, who has now crossed to the other shore, depends in part on whether I remember or forget him; he does not stop needing my love." 
Catholics are not the only ones who pray for the dead. The custom is also a Jewish one, and Catholics traditionally drew upon the following text from the Jewish Scriptures, in addition to some New Testament passages, to justify their belief: