The following are some of their main heresies:
According to their founder, Mrs. Ellen G. White,
“when Christ ascended to heaven he started to minister at the sanctuary of the celestial temple as the priests did in the terrestrial temple. For eighteen centuries he ministered in the first apartment of that sanctuary. Christ's blood assured the pardon and acceptance by the Father of the repentant believers, but their sins stayed in the records. It was necessary, she continues, for there to be an atonement work to remove the sin from the sanctuary, and this happened after 2,300 days, in 1844, when Christ would have entered the heavenly Holy of Holies to complete the last division of His work of purification of the sanctuary. Thus the sins of the repentant are put on Christ, who deposits them in the sanctuary. Later, before they are transferred to the Holy of Holies, to be extinguished completely, an investigation is made in the registries to determine who is entitled to the atonement, through repentance and faith in Christ (Compare with Leviticus 17:11; John 3:18; Romans 3:24; 8:1; Hebrews 9:22; 1 Peter 1:19).
This theory was invented to justify the non fulfilment of the prophecy of another founder of the sect, "prophet" William Miller, that had foreseen Christ's return categorically in 1844 (whence the name Adventist).
We have above the following heresies, with no Biblical basis:
a celestial sanctuary where Christ is chief priest
sins supposedly deposited in heaven
that in an inexplicable way the sanctuary is a type of mediator,
carrying the believer's sins for some time
that this sanctuary needs to be purified
that purification began in 1844.
They teach that Satan carries sins with Christ, and that he is the substitute that will take the repentants' sins with him when he is banished from the presence of God, being destined to cease to exist when sin and sinners are finally destroyed (compare with Ephesians 2:13; Colossians 1:20; 1 Peter 2:24; 1 John 1:7).
According to their doctrine the Lord Jesus, when he was born, inherited a sinful human nature (compare with Luke 1:35; John 10:30; Hebrews 4:15, 7:26; I Peter 2:22; 1 John 3:5.).
This is a heresy also adopted by some other sects, besides the Russelites. According to their theories, when dying physically, the soul and spirit of people are unconscious because they cannot "function" without the body (compare Luke 16:24-26, 23:43; II Corinthians 5:8; Ephesians 4:9; Philippians 1:23; I Thessalonians 4:14, 5:23).
Also like the Russelites, they teach that eternal punishment, in the sense of eternal suffering, doesn't exist: the impenitent sinners as well as Satan and his rebellious angels, demons, etc., are destined only to the annihilation, which consists in reducing them to nothing, so they cease to exist. For them, immortality, eternal life, or endless existence is all the same thing, and will only be granted to those who have salvation (it is obvious that life and existence are not the same thing, for instance, a chair exists but it doesn't have life!) (Compare with Hosea 13:9; Matthew 3:12; 5:29-30; 8:12,42; 12:32; 18:8-9; 25:46; 26:24; 27:20; Mark 3:29; 8:36; 9:43-48; Luke 12:4-5; 16:19-31; John 2:19; 3:36; 5:28-29; 1Thessalonians 1:10; 2Thessalonians 1:8-9; 1 Timothy 6:9; Hebrews 6:2; 10:26-31; 2 Peter 2:3-10,17; 3:6-9; Revelation 14:10-11; 19:20; 20:10-15; 21:8).
The Adventists try to force a Christian to submit to the yoke of the Law given through Moses, moving him away from the Grace of God. This accompanies their theories that, having materialized a sanctuary in heaven, they are forced to materialize everything else: besides a sanctuary in the heaven, with chandeliers, curtains, table of unleavened bread and ark, they had to include inside of the ark the two stone tablets with the Ten Commandments, and to exhort all of us to submit to them.
Mrs. White said she had a vision that she was high in heaven, and the Lord Jesus lifted the cover of the ark and it showed her the tablets of the law: the fourth commandment stood out of the other ones, appearing in the centre with a shining halo surrounding it!
They say that Christians are still under the Law of Moses, that they should keep even the smallest of their precepts, and therefore must keep Saturday holy. According to them, it was the Roman-Catholic Institution that changed the observance of the Sabbath (seventh day of the week) to Sunday (first day) in 364 AD.
However, in reality Saturday was given by God as a sign and a perpetual alliance between Him and the children of Israel (Exodus 31:12-18), the tablets with the commandments are called "ministry of death" and "ministry of condemnation" that, the Holy Spirit teaches us, disappeared before the permanent glory of the "ministry of justice" (Acts 15:10, 24, 28-29; Romans 6:14; 7:4,6; 14:5-6; 2 Corinthians 3:7-13, Galatians 5:18; Colossians 2:14,16), a new alliance of the spirit, not of the letter; the Sabbath never appears in the New Testament as something that should be observed by Christians. Sunday didn't substitute Saturday: being the first day of the week, in which the Lord Jesus rose again, Christians since the apostolic times met on this day to remember him in the “Breaking of Bread” (Acts 20:7, 1 Corinthians 16:2).