Denominations have most often come about due to differences in beliefs from others. Many of them started because of a great move of God at a specific time and place in history. Then, after many years, they became a religious organization that operates with their own identity, doctrinal beliefs, traditions, and legal hierarchy.
Some even claim they are the only "true" church, while others say they are a non-denomination even though they have 100's of churches under their "banner" that are required to operate by specific rules of conduct, doctrine, and procedures.
Others claim direct revelation from God, alleging that Jesus and/or angels visit(ed) them in person. Some of them have declared that they visit(ed) Heaven many times and have/had conversations with Jesus, the Prophets and Apostles, which also denigrates the authority of Scripture as they build an experience-oriented theology based on emotionalism and suffused in mysticism. Others claim they are a Prophet or Apostle and have divine authority to interpret or even change the Bible by adding to it.
Despite man-made religious nonsense that has caused wars over differences of belief and interpretation, some fundamental essentials are the absolute foundational truths of Christianity. The Bible warns its reader about accepting another Gospel than the one that the original Apostles witnessed and preached.
"if any man is preaching to you a gospel contrary to what you received, he is to be accursed!" (Galatians 1:8 NIV)
Monotheism - God, the Father
The Bible declares there is only one eternal God who always existed in eternity past and into eternity future in three persons (or in what is known as the Trinity), God the Father, God - the Son, Jesus Christ, and God - the Holy Spirit. He is love, all-powerful, all-knowing, does not change, holy, a spirit and truth. (Deut 33:27; Isa 44:6; 57:15; 1 Kings 8:27; 2 Chron 2:6; Ps. 147:5; Jer. 23:24; Acts 17:24-28; Hos 11:4; Jer 31:3; Mark 1:41; 10:16; 1 John 4:8, 10; Job 42:2; Ps 115:3; Jer 32:17; Matt 19:26; Ps 139:1-6; Isa 46:9-10; John 2:25; Ps 102:27; Heb 13:8; James 1:17; Ex 15:11; Ps 24:3; Isa 40:25; Hab 1:13; John 1:18; 4:24; 1 Tim 1:17; 6:15-16; Isa 44:8-10; 45:5; Num 23:19; Rom 3:3-4; John 14:1,2,6; Heb 6:18; Titus 1:2).
He is omnipresent throughout the Cosmos (Psalm 139:7-12; Jeremiah 23:24). He is neither pantheistic nor omni-permeate because He created all things out of nothing. The entire sum of reality, which is made up of time and eternity, Heaven and hell, light and darkness, is not a seamless one with God. He is not nature and does not permeate or fuse His being or presence with, or into, His creation, as He is holy and exists eternally separate from the temporal creation (Isaiah 40:18-22; Romans 1:19-23; Revelation 4:10-11).
Each member of the Trinity is all co-eternal and of the exact nature. One God in three persons means one personal multidimensional God who lives and works in three different ways simultaneously outside of all human-imposed knowledge, comprehension, and understanding restrictions (Exodus 20:3-6; Isa 43:10; 44:6, 8; 45:5,14,18,21-22; 46:9; 47:8; Deuteronomy 6:4). This doctrine is represented throughout the Bible and is arrived at systematically by looking at the totality of Scripture. It is the proper representation of scriptural revelation concerning the nature of God.
Jesus commands Christians to fulfill the Great Commission: "Go therefore and make disciples of all the nations, baptizing them in the name of the Father and the Son and the Holy Spirit" (Matthew 28:19 NIV - also 3:16-17; 1 Corinthians 12:4-6; 2 Corinthians 13:14; Ephesians 4:4-6).
God the Son, Jesus Christ
Jesus Christ is a member/part of the Trinity and is 100% fully human and 100% fully God, the Son, who came from a reality eternally separate from the Earth and willingly chose to come to earth as a human in the flesh, which gave Him the essential power to save anyone who repents of their sin and receives Him as Lord and Savior from the penalty of sin through His shed blood on the Cross (John 1:1; Col 1:15-19; 1 John 5:7-8; Luke 4:34; John 8:23-24; Heb 2:16-18; Matt 1:18; 4:2; Luke 2:40; John 4:6; 8:40; 11:35; 19:28). Heb 2:16-18; Matt 1:18; 4:2; Luke 2:40; John 4:6; 8:40; 11:35; 19:28). He had no beginning and no end (John 8:57-58). Jesus has been given all authority in Heaven and Earth.
The Old Testament was completed at least 300 years before the historical Jesus was born. There are over 350 predictions of His coming and ministry. No other person in history can meet the prophetic criteria. The mathematical probability of just 11 of those coming to pass is one chance in 10 to the 19th power - that's one chance in 10 billion times 10 billion!
Jesus had a virgin birth from a surrogate mother. He is not "a" god or the biological offspring of God or humanity (Matthew 1:18; Luke 1:35). He claimed the authority of God and is the Creator and the sustainer of all things (Mark 2:10; 14:6; John 6:39-40; 10:17-18; John 1:3; Hebrews 1:3; Col 2:9). The Bible foretold His birth, ministry, suffering, and death (Isaiah 7:14; 9:1-2; 52:13-115; 53; Jer 23:5-6; Psalm 16:10; 22; 41:9; 68:18; 69:21; Micah 5:2; Daniel 9:25; Zec 9:9; 11:12).
As a human, He relied on His divinity and the Father and Holy Spirit to perform miracles to prove He was fully God (Luke 4:18; John 10:33-39; Mark 4:35-41). He declared Himself the only way to salvation, did what only God could do, and voluntarily sacrificed His sinless life on the Cross to atone for the world's sins (John 14:6; 1 John 2:2).
The Claims of Jesus
Jesus is absolutely and distinctly different from every other religious leader who has ever lived. He is the only person in history who claimed to live a sinless life, be God, and share God's glory in Heaven (John 8:28-29, 46-47; Matthew 12:6,22:37; Mark 2:1-2, John 1:1-5, 17:5). When He was accused of claiming to be God, He did not deny it (John 10:30). Jesus did not correct the disciple Thomas when he said to Jesus: "My Lord and my God" (John 20:28 NIV). That is why He was put to death by the religious leaders of His day.
Jesus said that if a person believes in God, they should believe in Him (John 14:1). He also claimed to be the ONLY way to God and that He was able to forgive sins and give everlasting life, starting when a person chooses to make Him their Lord and Savior. He also prophesied that He would die and come back to life and return to judge the world (Luke 18:31-33; John 10:17,12;32-33,16:16; Matthew 24:27-30, 25:31-32; Mark 14:61-62).
Jesus willingly received worship and claimed the role and functions reserved only for the Creator God in the Old Testament, such as being the Shepherd, the Rock, and the Sower (Matthew 2:11, 7:24-27,13:24-30,14:33, 21:15-16; Luke 24:52; John 9:38; Luke 15).
Jesus declared that He had the same level of authority as God, that He existed before Abraham, and that He had the name of God (John 5:19; Exodus 3:13,14; John 6:35, 8:24,58-59,10:11-14,11:25). He also declared that He was the truth, the Lord of the Sabbath, and those who have seen Him have seen God (John 14:6,9; Matthew 12:60). Jesus said to the apostle John "I am the Alpha and the Omega,…who is, and who was, and who is to come, the Almighty" (Revelation 1:8 NIV).
The Eternal Word
Jesus, the eternal Word, possessed a full undiminished human nature and a full undiminished divine nature. Jesus is the complete word (Gk: Logos) and revelation of God made flesh (John 1:1). He did not regard equality with God as a thing to be grasped and emptied Himself as an act of divine humility to prove His love as He took on the "form of a bond-servant" while remaining 100% fully God (Philippians 2:5-8). Jesus, being God the eternal "I AM," did not empty Himself of His divine nature or give up some, several, or any of the divine powers and essential attributes of deity to assume the form of a servant and become incarnate as a human being. He said He would raise His body from the grave in the Resurrection (John 2:19-22; Acts 2:24,3:15, 4:10, 5:30; 10:40;13:30; Romans 8:11,10:9, 1 Corinthians 6:14, 1 Peter 1:21; Galatians 1:1). He did not become an indwelling Spirit. He has always been and always will be God, the Son. He willingly set aside the visible manifestation and exercise of His Glory as the Triune God and sometimes chose not to use His divine attributes. He wasn't confined to the form of a servant, nor did it limit him.
He continued to exercise His divine attributes when a situation demanded it. He demonstrated His Omniscience, Omnipotence, Omnipresence, Omnibenevolence, Providence, and Sovereignty because God's fullness dwelt in Him bodily during His earthly ministry! (John 1:48, 2:24-25, 5:21-23, 6:64,70-71, 10:17-18, 11:11-14, 43-44, 17:2, 18:5-6, 3:35,38; Matthew 11:27, 18:20, 28:18-20; Mark 2:28; Luke 7:14; Hebrews 1:1-3; Colossians 1:17,19-20)
Jesus did not give up His own essential holiness. In His prayer to the Father, He asked for the return of His Glory, but He did not ask for the return of His power or attributes because He already had them. He did not change because He was, is, and will always be "the same yesterday and today and forever" (Hebrews 13:8 NIV).
The Greatest Mystery
Jesus is a great mystery who, as a human being, loved, lived His life, and spoke like no other man has ever done or ever will (Romans 16:25, 1 Corinthians 2:7, Ephesians 1:9, 3:4, 3:9, Colossians 1:27). Through His act of ultimate humility, He willingly suffered and died on the Cross as wholly God and wholly as a human being. In His act of atonement, Jesus took all sins, past, present, and future, upon Himself, "For He made Him who knew no sin to be sin for us, that we might become the righteousness of God in Him" and defeated satan ultimately for eternity at the Cross (2 Corinthians 5:21 NKJV).
At the Cross, the entire Trinity was involved as the Father poured out His wrath, the Son paying the absolute price for the remission of sins as the final sacrificial lamb turning away the wrath, and the blood of Jesus offered through the Holy Spirit for the sins of all human beings (Romans 1:18,3:25-2,5:8-11; Hebrews 9:14). This is the greatest mystery that came directly through Love Himself. The blood of God was shed and poured out to redeem and set free all who willingly choose to accept Him as their personal Lord and Savior and become Born-Again by repenting of their sin and surrendering their life to Him (John 3:16; Acts 20:28).
Jesus intercedes from Heaven for all Born-Again Christians (Matthew 3:17,14:27; Mark 6:50; John 1:1; 1:14; 8:24,58; 10:30; Titus 2:13; 1 John 5:20). He is both love and the Word incarnate. He is the only mediator between God and humanity and is the proper and only object of a person's faith (See 1 Timothy 2:5). Salvation is found in no one else (Acts 4:12; Romans 10:9). He said that if a person does not believe He is God - the "I am" of the Bible - they will die in their sins (Exodus 3:14; John 1:1,14; 3:18; 4:2-3; 8:24,58; 10:30-33; 14:6; 20:28; Colossians 2:9; Philippians 2:5-8; Hebrews 1:8).
God, the Holy Spirit
The Holy Spirit is fully God, the pre-existent Counselor, and Comforter who lives inside every Born-Again Christian and will remain in them to help, guide, and change those who willingly want to be changed (Isaiah 40:13; 1 Corinthians 2:12; Psalm 139:7; Job 33:4; Romans 8:2; Galatians 5:22; John 14:17). He is not a "spirit guide," "pure energy," or a "ghost" or phantom. He has a will, mind, and feelings with His personality (1 Corinthians 2:10-11,12:11; Ephesians 4:30; Acts 16:6-11). He is not a raw power that exerts energy or the effluence of the eternal God that resonates through eternity. He is the third person of the Triune God (Genesis 1:2; Matthew 12:28, 31-32; 28:19; Acts 1:8).
He convicts of sin, performs miracles, intercedes for, and guides true Believers into truth by hearing, speaking, showing, and imparting spiritual gifts (John 16:8,13; Acts 8:39; Romans 8:26; 1 Corinthians 12:1-11). The Holy Spirit inspired the writers of Scripture and originates and energizes the love of God to lead and move the Born-Again Christian "deeper into God" in an intimate relationship and makes them a "partaker of the divine nature" (2 Peter 1:4 NIV). He is tasked to complete the "good work" in those who become Born-Again and "carry it on to completion until the day of Christ Jesus" (Philippians 1:6 NIV).
Salvation by Grace
Human beings cannot do anything to earn salvation. It comes only by faith in Jesus Christ and His shed blood on the Cross through repentance and conversion.
"For it is by grace you have been saved, through faith -- and this not from yourselves, it is the gift of God -- not by works, so that no one can boast" (Ephesians 2:8-9 NIV)
God's grace saves, and His mercy sustains the Christian every day. A human being cannot add to the work of God, nor can they be coerced or compelled to enter into the kingdom of God.
"I do not set aside the grace of God, for if righteousness could be gained through the law, Christ died for nothing!" (Galatians 2:21 NIV - See also 3:5, 31; Romans 3:5, 20, 4:5).
The Resurrection of Jesus
Jesus said, 'I am the resurrection and the life. He who believes in me will live, even though he dies; and whoever lives and believes in me will never die...'" (John 11:25 NIV). The physical resurrection of Jesus is at the very core of faith. Without the resurrection:
"…our preaching is useless and so is your faith"….. "And if Christ has not been raised, your faith is futile; you are still in your sins." (1 Corinthians 15:14,17 NIV - See also John 2:19-21).
The Gospel Message
Only Jesus alone has the power and authority to execute God's plans and purposes on Earth, clearly revealed in the Bible. The Gospel message is that Jesus is the Creator God in human flesh who did not give up His deity to become a human being, died for humanity's sins, rose from the dead, and freely gives the gift of eternal life to those who submit their life to Him (1 Corinthians 15:14). This absolute truth must be believed for a person to become a Born-Again Christian. If anyone - whether an angel or human "preach a gospel other than the one we preached to you, let him be eternally condemned" (Galatians 1:8-9 NIV). It would not be possible to present the gospel properly without declaring that Jesus is God in the flesh (John 1:1,14; 10:30-33; 20:28; Colossians 2:9; Philippians 2:5-8; Hebrews 1:8).
"For we did not follow cleverly devised tales when we made known to you the power and coming of our Lord Jesus Christ, but we were eyewitnesses of His majesty. For when He received honor and glory from God the Father, such an utterance as this was made to Him by the Majestic Glory, This is My beloved Son with whom I am well-pleased— and we ourselves heard this utterance made from Heaven when we were with Him on the holy mountain. So we have the prophetic word made more sure, to which you do well to pay attention as to a lamp shining in a dark place, until the day dawns and the morning star arises in your hearts." (2 Peter 1:16-19 NIV)