All faiths are paths to God. However, there is a direct co-relation between Jesus' statements "how few find the narrow gate to Heaven" and "you must be made perfect as the Heavenly Father" (Mt 5:48). Traditionally, Catholics believe in the continuing process of purification called Purgatory which Jesus seemed to have hinted in Mt 5:25-26 as "prison where you will not be released until you pay the last penny".
Why is Purgatory necessary when Jesus has redeemed us by His Blood? The answer to this lies in understanding sin. Sin is an offence against both God and man and, to be wiped clean, reconciliation must be made with God and man. If I, after murdering your child and escaping human justice, only begged divine forgiveness and was allowed into Heaven, you would hold my merciful God to be your unjust God. God who created the merciless and eternal hell certainly holds us accountable for our sins, even if it be an idle word against others. Jesus talks of punishment in Lk 12:46-48 and details the ways of perfection in Matthew chapters 5, 6, and 7.
Moreover, we are still bound to the Command of Love - of God and neighbour. Jesus' death has made divine reconciliation readily available. Human reconciliation, however, is often difficult or impossible. We carry the sinful burden of un-reconciliation when offended persons move away or when we envy or despise strangers.
David's adultery with Bathsheba and the subsequent murder of her husband, Uriah, is an example of divine forgiveness when David acknowledged his sin before the prophet Nathan (cf. 2Sam 12:13). However, as there was no way of reconciliation with the dead Uriah, David was warned that "the sword shall never depart from your house and your wives will be given to your neighbour" (2Sam 12:10-11).
The Good Thief was graced with serving his Purgatory on the cross. In Mk 13:19, Jesus stated that the last days would be unprecedented in human distress, a veritable "Purgatory on earth", when the "Rapture" or bodily ascension of many would occur.
Launched and led by the Holy Spirit for 2000 years, the Catholic Church has directed how our inconspicuous prayers, fasting and good works can --- both for ourselves and others --- merit Our Father's reward, downsizing our time in Purgatory. Apparently, the Catholic way provides the shortest path to God and to His superabundant reward in Heaven.
To be sure, the Eucharistic celebration of the Mass, the highest form of public worship, offers the greatest means by which we can shorten our Purgatory. Other efficacious means are The Way of the Cross, St. Bridget's Prayers, penance and almsgiving.
Catholics are unique in that, apart from their belief in Purgatory, they routinely pray for others also in the Divine Mercy Chaplet. This is truly "Love in Action" and a concern that other's salvation is as important and necessary as our own. Besides, we are aware that Our Lady is the celestial inhabitant who is allowed to visit and console those souls in Purgatory who while on earth had prayed to her.
Purgatory has the marks of perfect justice --- to the last penny --- and release after. In Hell true justice reigns but alas no release. On earth there is release but not true justice. Purgatory is therefore necessary because "God chose us to be holy and blameless in His sight" (Eph 1:4).
