Most people know that in our current arrangement, young men tend to receive the priesthood at age 12, when they are ordained to the office of Deacon in the Aaronic priesthood. This has been the case only since the 1880’s or so, according to this fascinating Journal of Mormon History article. (That page it opens to isn’t blank. You just have to scroll to see the text.)
What we don’t really have is a good definition of priesthood in terms of offices or ritual. For those readers mumbling “uh, yes we do,” let me confuse the issue for you.
First, we know that “priesthood” is not synonymous with “priesthood office,” according to D&C 107:1-5.
Second, in terms of etymology, “priesthood” means something like “the condition or status of being a priest; the order of priest.”
Third, the biblical way one becomes a priest is not by laying on of hands. (At least, we have no record of Aaron undergoing laying on of hands.)
Rather, according to Exodus 29 and Leviticus 8, it involves a ceremony of ritual purification, entering into sacred ground within the temple boundaries, being washed, anointed, clothed in priestly clothing, “filling the hand,” and some other things. We certainly don’t do that with 12-yr olds (anymore), although we do something similar with adults.
(It has been pointed out in print that if one goes by the Biblical standard, than the LDS Church has de facto female priests who are not ordained to any particular office.)
The OED notes in its definition of priesthood that it can also refer to “Priests collectively; a body of priests.” That certainly applies to the 12-year old, who, upon being ordained, joins that collective body of males. But it doesn’t provide us a good definition of priesthood with regard to the offices and LDS rituals.
Some of the semantic issue here is due to the LDS doctrine of priesthood as some kind of authority instead of priesthood as service (ie. teaching and performance of ritual). That is, the usual definition of priesthood given is “the authority to act or speak for God,” but that definition is not entirely consistent with the role of priests in the Bible. Nota bene, I’m not saying it’s wrong. I’m just saying that we view things differently today. Our view of priesthood (definition, responsibilities, offices) doesn’t map very well onto the OT, the NT or the Book of Mormon.
Food for thought.