From its beginning in 1849, the UCMS was never widely accepted among brethren. Not only was there strong objection to it, the churches simply refused to support it financially. It has even been questioned by some who have studied the Restoration Movement, if Alexander Campbell finally saw the truth about the UCMS. In his book "Foundation Facts and Primary Principles" G. C. Brewer, p.221, states that Alexander Campbell, (the first president of the Society, an office he retained until his death), left nothing to the society in his will when he died. He left $5000 to his home congregation to do missionary work, but nothing for the society.

While some looked upon Alexander Campbell as the founder of the society, they viewed W. K. Pendleton, his son-in-law, as its savior. From the beginning he was one of the society's staunchest defenders. Twice in the history of the UCMS, he was called upon by the society to deliver a speech in its defense during their annual convention.

Even though other arguments in defense of the society were made before and after his speech in 1866, what Pendleton said at that time contained the substance of almost every argument used to support it. Some may have expanded on some parts of the speech, but as far as the substance is concerned, little new can be found. Even today, those who seek to establish and maintain human institutions follow the substance of Pendleton's defense of the society.

One of the arguments used by opponents of the society was that in establishing the society the proponents had departed from "original ground." i.e. that it was unknown to the early restoration movement. Some were saying that it was a reversal of what Campbell had taught years earlier in his paper "The Christian Baptist." To the charge that it was a departure from "original ground" Pendleton freely admitted. He simply argued that to say the Missionary Society is wrong because it was unknown in the earlier restoration movement, is to follow human opinions. and this was contrary to the very genius of the movement. Suppose the early pioneers did have the opinion that it was wrong to support a society; that should not be binding upon all. He then charged the opponents had misunderstood what Campbell had written. He said Campbell's writings must be understood in light of the fact he was attacking the ABUSE by denominations, not the institution itself. Pendelton's reply was weak, and his prejudice showed through. He seemed to suggest that by opposing the society they were saying Campbell had been opposed to doing missionary work. This was not true. None of the opponents ever charged Campbell with opposing missionary work in his earlier writings, they were simply opposing the PLAN of doing it through a human institution such as a missionary society. Students of the restoration movement today can read how thoroughly Jacob Creath Jr and David Lipscomb pointed out in their writings that the things Campbell advocated in "The Christian Baptist" in which he opposed human institutions and societies, were contrary to that which he later wrote in the "Millennial Harbinger" where he encouraged them. But in none of their writings did the opponents ever suggest that Campbell had been opposed to missionary work.