Prayer – Why do it?

In his Institutes of the Christian Religion, John Calvin addresses why anyone should pray to God:

For there is a kind of [communication] between God and men, by which, having entered the upper sanctuary, they appear before Him and appeal to his promises, that when necessity requires they may learn by experiences that what they believed merely on the authority of his word was not in vain.

Now, he takes as a given that we hold to this:

Without faith it is impossible to please him, for whoever w...