Blessings are a pretty common thing in the LDS Church. Soon after a baby is born, the parents give the new child a blessing. Once the child is baptized, another blessing is bestowed to give the child "the gift of the Holy Spirit." Young men are given several blessings as they advance through the various levels of priesthood. Blessings are given, as needed, to those who are sick or have other troubles in their lives.
But of all these blessings, none is more interesting or more important to many members than their patriarchal blessing. Members of the LDS Church first began receiving such blessings when Joseph Smith Sr. was called by his son to administer them. From a doctrinal standpoint, the first recorded patriarchal blessing was given to Abraham by Melchizedek after his return from the slaughter of Chedorlaomer (Gen. 14:17-40 JST). The first person actually eligible for such a blessing was Cain, but if such a blessing was ever given, it wasn't recorded.
There are a few differences which distinguish a patriarchal blessing from most other blessings. Unlike a father's blessing, blessings by patriarchs are generally once-in-a-lifetime endeavors. Barring unusual circumstances, it won't be repeated. Also, this is the only blessing where a person will be informed of their "lineage," which refers to the tribe they descended from. Invariably, the recipient will discover that he is of the lineage of Ephriam or Mannasseh. At least, I've never heard of any exception. Of course, mistakes are made, and the child of two Ephriams will sometimes be declared a Mannasseh. The most common explanation given for this phenomenon is that the blood of the two tribes has been so completely mixed that everyone contains a certain amount of both, and that the lineage only refers to the nature of the blessing and not to any literal descent.
Usually, the blessing is received at some point during the teenage years. Short of a temple marriage or a mission call, no milestone in a young LDS life is more significant than receiving this blessing. The process of receiving such a blessing is actually rather simple: after an interview with the bishop to ensure the worthiness of the blessing candidate, an appointment is made with the stake patriarch. The actual blessing is a subdued affair, usually involving only immediate family members (and possibly one or two close friends). The patriarch asks a few questions about the candidate's current dreams and goals. Ostensibly, this method of pleasant interrogation is to help foster the Spirit. From an outsider's standpoint, it appears more likely that the patriarch is simply trying to find out enough to make the blessing sound less like what it is: a collection of vague predictions and random guesses by a total stranger.
Speaking as someone who has experienced the process firsthand, but had difficulty seeing the process "through the eye of faith," I saw very little inspiration in the entire process. The entire blessing felt entirely impersonal, almost as though the blessing could have been given, with a very few modifications, to any male member of the Church. Worse, the same patriarch also gave my brother his blessing, and when I later compared them, they were in almost every respect the same. Though many find their blessings to be a source of inspiration, in my case it was one of a few critical junctures which eventually led to my leaving the Church.
Below is a growing collection of patriarchal blessings from the early days of the Church and more recent times. My ultimate goal is to document just how drastically the tone of these blessings, and LDS expectations about the future, have changed.
My Patriarchal Blessing
The Patriarchal Blessing of Joseph Smith (off site).
Excerpts from Early Church Blessings (off site).
The Patriarchal Blessing of Wilford Woodruff
A Patriarchal Blessing given to Wilford Woodruff Jr.
Virtual Patriarchal Blessings from latterdaylampoon.com
Patriarchal Blessings: As explained by www.mormons.org.
Patriarchal blessings on the Recovery From Mormonism site:           
How to get a copy of your patriarchal blessing.
1) In an official statement written by David O. McKay, Stephen L.
Richards, and J. Reuben Clark, Jr., the First Presidency states, "Patriarchal blessings
contemplate an inspired declaration of the lineage of the recipient. . ." (June 28, 1957,
in a letter to all stake presidents. Quoted in Bruce R. McConkie's Mormon Doctrine)
While this usage implies literal genetic descent, it is one of the few statements I've found
which doesn't note the possibility of adoption. It was also interesting to note that, in McConkie's
Believing Blood entry, he claims that "those spirits who in the pre-existence developed an
especial talent for spirituality and for recognizing truth," are generally sent to families
where there is a high concentration of the blood of Ephriam.
2) "A man whom the stake president recommends as stake patriarch should be a worthy Melchizedek Priesthood holder. He should be mature in the gospel and the Church, a worthy patriarch in his own home, and sensitive to guidance from the Spirit. He should have received his own patriarchal blessing, and normally he should be age 55 or older." -Church Handbook of Instruction, 1998 edition
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