23. Do Adventists claim they have ‘the truth’ and that the SDA Church is the one true and exclusive Church?

No and No. This is another commonly cited ‘proof’ that the Seventh-day Adventist Church is a cult.  Again, with many of these issues, the application of Christian jargon can be slight but very important.  This commonly leads to confusion over terminology rather than substance.  The Seventh-day Adventist position is actually similar to those held by other ‘orthodox’ denominations, including the Roman Catholic Church, Eastern Orthodox Churches and even the Assemblies of God (the largest Evangelical-Protestant denomination).  Therefore, critics should be careful to judge Adventists by those same standards and not by imagined, inconsistent and arbitrarily applied criteria.

As outlined in SDA fundamental belief #13:

“13. The Remnant and Its Mission:

The universal church is composed of all who truly believe in Christ, but in the last days, a time of widespread apostasy, a remnant has been called out to keep the commandments of God and the faith of Jesus. This remnant announces the arrival of the judgment hour, proclaims salvation through Christ, and heralds the approach of His second advent. This proclamation is symbolized by the three angels of Revelation 14; it coincides with the work of judgment in heaven and results in a work of repentance and reform on earth. Every believer is called to have a personal part in this worldwide witness. (Rev. 12:17; 14:6-12; 18:1-4; 2 Cor. 5:10; Jude 3, 14; 1 Peter 1:16-19; 2 Peter 3:10-14; Rev. 21:1-14.)”

See: http://www.adventist.org/beliefs/fundamental/index.html

Regarding the first part of the question, Adventists might say they are a unique remnant people with a special message, having the most truth as found in the Bible, but probably not the truth. As with most Christian traditions, the SDA Church has not officially or historically ever held that it possesses all ‘the truth’, in the sense of a final and complete knowledge of God.  As further stated in the preamble to the 28 SDA Fundamentals:

“Seventh-day Adventists accept the Bible as their only creed and hold certain fundamental beliefs to be the teaching of the Holy Scriptures. These beliefs, as set forth here, constitute the church's understanding and expression of the teaching of Scripture. Revision of these statements may be expected at a General Conference session when the church is led by the Holy Spirit to a fuller understanding of Bible truth or finds better language in which to express the teachings of God's Holy Word.”

Thus, the SDA Church almost uniquely amongst Christendom has no formal creed other than the Bible (2 Tim 3:16), and recognises the principle of present and progressive scriptural truth (2 Pet 1:12).  As stated by SDA pioneer Ellen White:

“And the years of eternity, as they roll, will bring richer and still more glorious revelations of God and of Christ. As knowledge is progressive, so will love, reverence, and happiness increase. The more men learn of God, the greater will be their admiration of His character.” (Ellen White, Mar 373.2, emphasis added).

Much like the Early Church, Adventists have a long history of openness and evolution of theological thought, recognising that on earth we at best “now see only a reflection as in a mirror” (1 Cor 13:12).  Even within Adventism, there is a wide spectrum of different positions, from conservative ‘Historical Adventists’ to liberal ‘Evangelical Adventists’:

See: http://en.wikipedia.org/wiki/Historic_Adventist

And: http://en.wikipedia.org/wiki/Progressive_Adventist

In fact, some outside Christian commentators have even criticised this commitment to progressive scriptural understanding and tolerance of divergent views, as it has arguably prevented the SDA Church from communicating to outsiders what ‘the official position’ of Adventism is on a range of subjects:

“Because of Adventism's strong emphasis on progressive scriptural understanding, they have been reluctant to adopt any formal creed. Even their doctrinal statement known as the "27 Fundamental Beliefs" allows for change and revision. Historically, this lack of a formal creed and emphasis on progressive biblical understanding has given place to a wide spectrum of doctrinal interpretation among Adventists. In the 1950s, as today, this tolerance of divergent and sometimes heretical views has hurt the unity and doctrinal soundness of their denomination. This was a critical issue for the evangelicals, who could not hope to accurately represent the position of Adventism to the evangelical world if the Adventists themselves lacked consensus as to those positions.” (emphasis added)

See: http://www.iclnet.org/pub/resources/text/cri/cri-jrnl/web/crj0005b.html

In relation to the second part of the question regarding the one and exclusive Church, Adventists make the slight but important distinction between the Church at Large, comprising all individual believers found a multiple of Christian denominations, compared with the remnant role of the Seventh-day Adventist movement.  This is a position found in many other ‘mainstream’ Christian groups, who no doubt each believe their denomination has a special mission.

For example, the Roman Catholic Church teaches in the Second Vatican Council Dogmatic Constitution Lumen gentium, that there is only one Church, where certain non-Catholic communities can on some level form part of the body of Christ.  However, the only one Church is said to ‘subsist’ in the Catholic Church alone:

"Christ “established here on earth” only one Church and instituted it as a “visible and spiritual community… This Church, constituted and organised in this world as a society, subsists in the Catholic Church, governed by the successor of Peter and the Bishops in communion with him…It is possible, according to Catholic doctrine, to affirm correctly that the Church of Christ is present and operative in the churches and ecclesial Communities not yet fully in communion with the Catholic Church, on account of the elements of sanctification and truth that are present in them. Nevertheless, the word 'subsists' can only be attributed to the Catholic Church alone precisely because it refers to the mark of unity that we profess in the symbols of the faith (I believe... in the 'one' Church); and this 'one' Church subsists in the Catholic Church." (emphasis added)

http://www.vatican.va/roman_curia/congregations/cfaith/documents/rc_con_cfaith_doc_20070629_responsa-quaestiones_en.html

Moreover, the Eastern Orthodox Church also considers itself the “One Holy Catholic and Apostolic Church, founded by Jesus Christ and His apostles”.

            See: http://www.saintignatiuschurch.org/orthodoxchurch.html

Even the official statement from the North American Assemblies of God (the largest Evangelical-Protestant denomination) likewise makes the distinction between spiritual unity of the Church at Large, compared with its institutional separation from other denominations:

“The New Testament is clear in its teaching that there is only one Church, which is described as the body of Christ (Eph. 1:22,23; 2:16; 4:4; Col. 1:13-21; Rom. 12:4,5; 1 Cor. 12:12-20). That one Church includes all who have accepted Jesus Christ as Savior and are serving Him as the Lord of their lives. It is also clear that Jesus’ desire for the Church is that all believers be one, even as He and the Father are one (John 17:11). The unity for which Jesus prayed comes obviously from His redemptive work on the cross (Eph. 2:16). It is a spiritual unity rather than an institutional unity.

...Unity in the body of Christ does not require accepting the beliefs and practices of any group that offers membership to enhance cooperation on social and legislative matters. The Assemblies of God has historically been cautious in making alliances with church groups that do not hold the same biblical priorities, but rather emphasize social concerns over the importance of changing lives through a genuine salvation experience.” (emphasis added)

See: http://ag.org/top/Beliefs/topics/sptlissues_church_at_large.cfm

Finally, one of the main reasons the SDA Church is perhaps wrongly accused of being exclusive, is that unlike many other protestant churches (which are often merely national churches), but similar to the Roman Catholic, Eastern Orthodox and Evangelical-Pentecostal Churches described above, the Seventh-day Adventist Church holds itself to be a universal Church (i.e. literally ‘Catholic’).  As outlined in fundamental belief #14:

“14. Unity in the Body of Christ:

The church is one body with many members, called from every nation, kindred, tongue, and people. In Christ we are a new creation; distinctions of race, culture, learning, and nationality, and differences between high and low, rich and poor, male and female, must not be divisive among us. We are all equal in Christ, who by one Spirit has bonded us into one fellowship with Him and with one another; we are to serve and be served without partiality or reservation. Through the revelation of Jesus Christ in the Scriptures we share the same faith and hope, and reach out in one witness to all. This unity has its source in the oneness of the triune God, who has adopted us as His children. (Rom. 12:4, 5; 1 Cor. 12:12-14; Matt. 28:19, 20; Ps. 133:1; 2 Cor. 5:16, 17; Acts 17:26, 27; Gal. 3:27, 29; Col. 3:10-15; Eph. 4:14-16; 4:1-6; John 17:20-23.)” (emphasis added)

In conclusion, the Seventh-day Adventist Church is no more exclusive or cult-like than many other ‘mainstream’ and ‘orthodox’ Christian denominations.  To the extent that Adventists believe they belong to a universal Church commissioned with a special and remnant truth for the whole world, they are undeniably unapologetic.  This does not, however, make them a cult.