http://atheism.about.com/library/glossary/western/bldef_calvinism.htm

Calvinism is the Protestant theological system designed by John Calvin (1509-1564). Calvinist theology is often labeled "federal" or "covenantal." According to this perspective, God has made to agreements or covenants with humanity, both of which are important when it comes to understanding human history.

Usually divided into the following doctrines:

1.Total Depravity (Inability) refers to the fact that human sin has affected every aspect of the human character – thought, emotions, will, etc.

2.Unconditional Election is the doctrine which teaches that God chooses some to be saved and some to be damned. These choices are not, however, based upon any acts performed by those people or any merit which they have achieved (otherwise, there would be a violation of the principle of Total Depravity).

3.Limited Atonement is a concept which teaches that Christ died for the sins of some (those predestined to heaven), but not for others (those predestined to hell).

4.Irresistible Grace refers to the fact that when God has bestowed his grace upon a person because they have been predestined for heaven, it is impossible for a person to "resist" this grace and not end up in heaven. No matter what they do and no matter what they think, they are saved.

5.Perseverance of the Saints is the doctrine which argues that the saints (i.e., those whom God has saved) will always remain under God’s protection until they are brought to heaven. In other words: Once a Saint, Always a Saint.

The above doctrine puts believers in a catch 22 situation. Why bother being good? Usually phrased as:

You can and you can’t,
You shall and you shan’t;
You will and you won’t.
You’re damned if you do,
And damned if you don’t.

Some of the more controversial of John Calvin’s quotes:

(source different from above.)

Let it stand, therefore, as an indubitable truth, which no engines can shake, that the mind of man is so entirely alienated from the righteousness of God that he cannot conceive, desire, or design any thing but what is wicked, distorted, foul, impure, and iniquitous; that his heart is so thoroughly envenomed by sin that it can breathe out nothing but corruption and rottenness; that if some men occasionally make a show of goodness, their mind is ever interwoven with hypocrisy and deceit, their soul inwardly bound with the fetters of wickedness.

Who will venture to place the authority of Copernicus above that of the Holy Spirit?

[Those who assert that] the earth moves and turns … [are motivated by] a spirit of bitterness, contradiction, and faultfinding; [possessed by the devil, they aimed] to pervert the order of nature.

John Calvin lived during the waning years of what has been labeled the Dark Ages. During this time religious zealots were resisting the discoveries of science. In particular they were raging against the discovery that Earth was not the center of the Universe, and that it moved, rotated, and indeed, circled the sun instead.

In many ways the ideas espoused by John Calvin rendered Christianity a hardy blow. People were helpless to change their fate, so why adhere to the restrictive rules of a belief system since if they were predestined to go to either heaven or hell they could do nothing to change it. Under the ideas put forth even many members of the churches could be predestined to hell and no matter the effort to alter the course of events hell is where they would go. Each and every parishioner was expected to behave as if they were one of the “chosen” ones never knowing whether they were chosen or not until they landed at the side of god or in a fiery pit of sulfur.