Doctrine and Covenants 84:4 said that the New Jerusalem and the temple would be built "in this generation" by the gathering saints.  It has not been built yet.  More than 143 years have gone by since that prophecy was given.  Even granting the extended (and unprecedented) concept of 100 years in a generation (4 Nephi 18, 22), the time for completion is long overdue.  The gathering of saints to Zion has stopped, and Brigham Young, Orson Pratt, and other General Authorities of the time all taught that "this generation" clearly meant the generation alive in 1832.  But they have all passed away.  The question is, how can one escape the conclusion that Joseph was a false prophet as is required by the test of a true prophet found in Deuteronomy 18:20-22, unless Brigham Young is the one who is the false prophet?

Response by John A. Tvedtnes (FARMS)

The revelation can be read as either a commandment or a prophecy.  If it is a prophecy, we have the same problem with the use of the term "this generation" found in Jesus' prophecy in Matthew 24:34, which also refers to events which have not yet been accomplished.  We know that there are people from Jesus' time (and Joseph Smith's) who are still alive, including John the Revelator and the three Nephite disciples, not to mention Enoch, Melchizedek, Elijah and others. 

If the revelation is a commandment rather than a prophecy (as I believe), then it is a commandment that was simply not followed because the Latter-day Saints were forcibly driven from the Independence region.  That it was a commandment and not a "failed prophecy" is indicated by the Lord's words to Joseph Smith in D&C 124:49-51:

"Verily, verily, I say unto you, that when I give a commandment to any of the sons of men to do a work unto my name, and those sons of men go with all their might and with all they have to perform that work, and cease not their diligence, and their enemies come upon them and hinder them from performing that work, behold, it behooveth me to require that work no more at the hands of those sons of men, but to accept of their offerings.  And the iniquity and transgression of my holy laws and commandments I will visit upon the heads of those who hindered my work, unto the third and fourth generation, so long as they repent not, and hate me, saith the Lord God.  Therefore, for this cause have I accepted the offerings of those whom I commanded to build up a city and a house unto my name, in Jackson county, Missouri, and were hindered by their enemies, saith the Lord your God."

That the Lord can change his mind when men act contrary to his will is reflected in Jeremiah 18:7-10:

"At what instant I shall speak concerning a nation, and concerning a kingdom, to pluck up, and to pull down, and to destroy it; If that nation, against whom I have pronounced, turn from their evil, I will repent of the evil that I thought to do unto them.  And at what instant I shall speak concerning a nation, and concerning a kingdom, to build and to plant it; If it do evil in my sight, that it obey not my voice, then I will repent of the good, wherewith I said I would benefit them."

Interestingly, the prophecy in D&C 84:5 was fulfilled at the dedication of
the Kirtland Temple in March, 1836, according to the journals of many then
present.