So, let us consider the historical context of anointing of the sick. In the years before Vatican II, the Roman Catholic church often referred to the sacrament of the anointing of the sick as Extreme Unction. 'Unction' is derived from the Middle English derivative of the Latin ūnctiōn (stem of ūnctiō ), which means anointing or besmearing. To be really technical: equivalent to ūnct ( us ) (past participle of ung ( u ) ere which means to smear, anoint) + -iōn. Likewise, the term 'Extreme' comes from the Latin legal phrase in extremis, which literally means 'in extremity,' which was a euphemism for 'at the point of death.'
The first known use of the actual phrase 'Extreme Unction' comes from the works of Peter Lombard, a Medieval theologian who died around AD 1160. He simply makes mention of the term and never claimed to have coined the phrase; so, historians assume the term was in common use by that point. Likely the term was coined when the Church in the Western was clearly staking out and defining what the 7 Sacraments of the Church were around the year 1000. Eastern Orthodoxy has a sacrament of Anointing the Sick (usually performed by more than one priest except in extreme circumstances) has never used the term 'Extreme Unction.'
What is historically likely, as is the case with most sacraments, is that anointing was done over the ill in the local congregation in the first centuries, much like what is described in the Epistle of James and elsewhere in the Bible. This evolved into something done for the extremely ill as Christianity grew and became a more formalized religion. By the Middle Ages when a very compartmentalized and formal ideal of the 7 sacraments and their form as milestone markers on the path of life took hold in the West, Anointing became Extreme Unction only for the dying. With sacraments like Baptism at birth, Confirmation evolving to a passage into adulthood, and Marriage/Holy Orders for adults, Unction became part of those "Last Rites" that were performed at the end of life.
The Roman Catholic church since the Second Vatican Council in the late 1960s rethought that entrenched ideal of Extreme Unction and reverted to an earlier understanding of Unction as Anointing of the Sick. In fact, any sick person can request prayers and anointing, even if their life is not in danger.
The Catechism of the Catholic Church (#1532) currently teaches:
"The special grace of the sacrament of the Anointing of the Sick has as its effects:
- the uniting of the sick person to the passion of Christ, for his own good and that of the whole Church;
- the strengthening, peace, and courage to endure in a Christian manner the sufferings of illness or old age;
- the forgiveness of sins, if the sick person was not able to obtain it through the sacrament of penance;
- the restoration of health, if it is conducive to the salvation of his soul;
- the preparation for passing over to eternal life."
Now, one will notice the tension in that definition. There certainly is baggage there of the old ideal of "Last Rites" and "Extreme Unction" as that sacrament for the dying. The current American Book of Common Prayer also carries this baggage, as the current prayerbook came out just a few years after Vatican II. This was a time when sacramental understandings were in flux, even in the Episcopal Church. Whereas Rome basically did away with the parlance of calling the sacrament of anointing "Last Rites," the Episcopal church has been much more loathe to completely abandon the idea of "Last Rites," as the 1979 Prayerbook has a section for the anointing of the sick, as well as a section with a litany and liturgy specifically for the dying. That section of the prayerbook is very fuzzy as to what section pertains to clearly the living and what pertains clearly to the dying. The rubrics for the priest to follow are very vague, and practically speaking, I am forced to mix and match some of those resources from situation to situation because that section of the BCP on Extreme Unction/Last Rites/Anointing of the Sick is not user friendly for clergy, mainly due to this rethink on the idea of "Last Rites."
That section is so confusing, in fact, that the Episcopal Church has even published a supplement on Prayers and Liturgies for the Dying in the 2nd Enriching Our Worship series that was suppose to help clarify that pastoral office that the 1979 BCP completely muddled. Interestingly, all previous editions of the Book of Common Prayer have had separate prayers and/or liturgies for the death of a child (as opposed to the death of an adult). The optimism in medical science in the mid-1970's led people to believe that there would seldom need to be liturgies for the death of children in the future, so there are virtually no resources about that in the current 1979 BCP. Sadly, this optimism as not panned out, which is a big part of the EOW supplement that came out a few years ago.
I personally refuse to use much of the EOW resources because they are invariably coupled with radical inclusive language and notoriously bad theology. As such, I use my own form of "Last Rites" that follows the general outline and prayers in the BCP, but I also add a few "old school" prayers, particularly the old Latin 5-fold form of annointing of the body. People still request "Last Rites," and I feel disengenuous not actually administering "Last Rites" in lieu of the confused form in the 1979 BCP, particularly if a grieving family has pastorally requested them. (This is what my parish gets for hiring a retro-grade Anglo-catholic.)
Going back to the Catholic definition of Anointing of the Sick from the catechism, one will also note, particularly if one is of a Protestant persuasion, of the notions of forgiveness of sins, which seem to be apart from the idea of anointing and praying for healing from physical ailments. The original question that was posed to me had to do with what anointing of the sick has to do with the absolving of sins. This goes back to the idea that the term "Last Rites" is plural and not singular. Confession, Bible study, and the Eucharist are also contained in the Last Rites.
One will also note in the Catholic Catechism definition above, that unction is for the "restoration of health, if it is conducive to the salvation of the soul." In this, I am in complete agreement with Rome. Last Rites is also a process of discernment of God's will. If a person is physically healed but that means the person will simply go back to drinking and smoking and carrying on in a sinful lifestyle and not give God another thought, then maybe physical healing is not what the person needs.
Anointing of the sick, however, does not simply include physical ailments. Sickness also comes in the form of spiritual sickness, which can include sins that poison the soul just as a cancer or other illness can poison the physical body. As such, I am in complete agreement with Rome on the idea that anointing of the sick is not simply a matter of praying for the restoration of physical health. Hence, again, recall the definition of a sacrament: an outward and visible sign of an inward and spiritual grace. Anointing of the sick is an act whereby we pray for the whole health of the individual, not just the spiritual. Part of that act has to do with the forgiveness of sins and setting a person back into full communion with God.