The Aaronic priesthood is described as "preparatory." I used to assume this implied the duties performed by deacons, teachers, and priests were meant to prepare them for greater responsibilities when they were ordained as elders. This may be part of the meaning of "preparatory," but I have come to see another meaning. The ordinances performed by deacons, teachers, and priests are preparatory for the greater ordinances of the Melchizedek priesthood. Baptism, the sacrament, and ordaining other priests, teachers, and deacons are all ordinances performed by the authority of the Aaronic priesthood, and they are all preparation for something greater. Baptism represents birth, among other things; it is the gate through which we enter the path to God, not the end of the line. The sacrament is an ordinance for those who are on the path, and its language is tentative. We only witness that we are willing to do certain things; we do not actually promise anything yet. Of course, to ordain someone to any office below that of Elder is to give them less authority than they will ultimately have if they continue faithful on the path.
John the Baptist was also sent to "prepare the way of the Lord." "John answered, saying unto them all, I
indeed baptize you with water; but one mightier than I cometh, the
latchet of whose shoes I am not worthy to unloose: he shall baptize you with the Holy Ghost and with fire..." (Luke 3:16).
Aaronic duties are also physical. Collecting fast offerings, setting up the sacrament and administering it, running errands for the bishop, and seeing to the physical needs of members via home teaching as representatives of the bishop, are all physically oriented tasks. They are visible, outward things.
Melchizedek priesthood ordinances are geared toward the spiritual, inward, invisible aspects of the gospel. A priest may baptize, but only an elder can confirm new members and bestow the gift of the Holy Ghost. Temple ordinances are all performed by elders, and they are not made public, but are hidden from the world to keep them sacred. You can watch someone immersed physically in water, but can you tell whether they have the broken heart and contrite spirit necessary to receive baptism of fire and of the Holy Ghost? Can we tell if they have the Spirit or not? This is the province of the Melchizedek priesthood.
In our backward telestial world, truth is mutable, expendable, and frequently tortured and mutilated for the purpose of salesmanship and deception. Three dimensional objects and social status outweigh truth in most circles here on earth. In heaven, however, the truth is in charge, and physical things are ancillary. The world could not be created until Jesus said, "Here am I, send me." His honest agreement to fulfill the role of Savior, was necessary in order for creation of the physical worlds to begin. Can you weigh words? How much mass does abstract information have? Can you drink a gallon of truth? Eternity and galaxies and trillions of inhabitants on millions of worlds hung on the word of one Being.
Just as this ranking of truth above physical concerns is the proper order for the universe, so it is the proper order for our internal worlds, our hearts, minds, spirits, and bodies. When the intelligence in us rules, when our spirits take the reigns, and our bodies are taking orders from them, all is well. When the body gives orders to the spirit, all is lost. It is not unlike a horse trying to ride a human. The human suffers, and neither of them get anywhere. As my mission president observed, the body is a wonderful servant, but a horrible master.
The world reflects the gross order of appetite before truth, and the Savior was confronted by the classical temptations of the world when He was in the wilderness. Bread represented the lusts of the flesh; leaping from a pinnacle of the Temple represented popularity; the vision of all the kingdoms and money of the world represented the twin temptations of wealth and power (can you have one without the other?) He faced down all of these, and triumphantly declared, "These things I have spoken unto you, that in me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world." Why should I be of good cheer if I'm still in the muck of this world, while He has slogged through and escaped? Because we rely on His merits. We do not merit (earn) anything, because we fall short; He merits everything, because He succeeded. He wants to share it with us, and has set the example for us to follow, as well as constructing the pathway to walk, making it possible to follow Him.
It seems to me that in the Old Temple, we get an image of worldly work from the Table of Shewbread. Bread is the byproduct of civilization. It requires work, knowledge of calendars and seasons, tilling, sowing, irrigation, harvesting, threshing, grinding in the mill, baking in ovens, in order to be enjoyed. By the sweat of our brow, and the cunning of our ingenuity, we eat bread. Meanwhile, we dodge the missiles of Satan. Money can procure bread; dishonesty, a blatant disrespect for truth, is the quickest path to money. Money is nothing but a paper promise of value, a promissory IOU. Liars can manufacture these in unlimited quantities. It is all very telestial, survival of the fittest, dog-eat-dog, predatory stuff.
But as you cross from your right to the left side of the Old Temple, in contrast to the Table of Shewbread, you find a golden, glowing representation of the Tree of Life, the Menorah. Lehi and his family "fell down" to partake of the fruit of this tree; there was no planting, plowing, reaping, etc. They merely came up to it and plucked the fruit. Many people in the Book of Mormon had spent their lives toiling in sin or in righteousness, but the moments when they crossed that line do not record effort on their part, other than to cry unto the Lord with all their hearts (see Mosiah 4:2-3, Alma 36:18-21, 22:15-18). The obstacles to the Tree in Lehi's dream were emotional, social, and only physical insofar as temptations are physical. There were mists, mockers, distractions, but no walls, barriers, or mountains in the way. Social constraints are not physical; they exist inside of us as inhibitions, a deep concern for others' opinions. Even the physical temptations, the mists of darkness, were options rather than compulsion; you could hold the rod to defeat them. The iron rod was a representation of the word of God, and His word is truth (John 17:17).
I have implied that truth is an abstract, weightless, zero-dimensional concept, an untouchable wisp or figment of consciousness. But Jesus claims it as a name for Himself: "...I am the...truth..." (John 14:6). He does not say "I am honest," or "I am truthful;" He says he IS the truth. The order of heaven is backwards from the order of this world in many ways, and the contrast between the disregard for truth and honesty here on earth are starkly contrasted against the strict obedience to truth, regardless of the inconvenience, pain, burdens, or suffering it may incur. Jesus embodies truth in that way; He was perfectly humble, always deferring to truth in spite of any consequences.
John was the living embodiment of the Aaronic priesthood, and Jesus was the living embodiment of the Melchizedek priesthood. John said, "He must increase, but I must decrease" (John 3:30). We emphasize the fact that God is a resurrected man, with a perfect body, but He also has a spirit. "God is a Spirit: and they that worship him must worship him in spirit and in truth." (John 4:24). There is a verse, D&C 93:19, that baffles me: "I give unto you these sayings that you may understand and know how to worship, and know what you worship, that you may come unto the Father in my name, and in due time receive of his fulness." The word "truth" appears eighteen times in that section of the D&C. I guess I am asking out loud rather than stating for sure, but is that related to the what mentioned here? I will leave this one hanging for now.