John Calvin (1509-1564) was a French-Swiss theologian who is generally considered to be the greatest and most influential Christian teacher of the second millennium.
Calvin's life's work, the 'Institutes of the Christian Religion' is one of the most important summaries of Christian practice of all time.
His religious administration and organization of the city of Geneva in Switzerland is the model for many millions of Christians worldwide today, especially the system of Presbyterian Church structure that the national Churches of Scotland and the Netherlands as well as countless others are based on.
Calvin followed Martin Luther's exposure of the Roman Catholic Church as fraudulent, corrupt and apostate, and made it his life's work to define Christianity as simply and clearly as possible so that such apostasies and departures from its true meaning would not be possible in the future.
Calvin's theology has been summed up by the acronym TULIP:
1. Total Depravity
That all people are lost in sin without God's salvationThat those saved are saved eternally, those condemned eternally condemned
2. Unconditional Election
That God alone chooses whom to save and whom to condemn
3. Limited Atonement
That Jesus Christ died only for those whom God chooses to save
4. Irresistable Grace
That salvation is by God's will not the individuals and cannot be resisted
5. Perseverance of the Saints
The Bible as the only authority on God's willJustification is by Faith alone
Soli Deo Gloria
All Glory is God's alone
Salvation is by Christ's work alone
Salvation is by Grace alone, not works
Calvin became the leader of the Church in Geneva in 1536, and set about making it the primary Christian theocracy in all of Europe. His system of Church organization became known as Presbyterianism.
No longer were single individuals made 'kings' and 'sub-kings' of Churches under their control as in the episcopalian system of Bishops. Instead local Churches elect representatives to Councils of Elders called Consistories in Geneva, generally known as Presbyteries in English. These Councils oversee individual Church ministers and their Councils (Sessions), and are overseen themselves by higher Councils meeting less frequently called Synods and General Assemblies.