This book stems from systematic theology lectures. Christology covers the eternal plan, the solemn promise, and accomplishment of salvation. God expresses his solemn promise of salvation in his covenants.
The first half of the book surveys Reformed Theologians/Theology such as the Westminster and London Confessions, John Gill, Charles Hodge, Robert Lewis Dabney, the Dutch Calvinists and contemporary modifications. This is extremely helpful for Nichols shows the many insights and contributions each have given to this area, but Nichols is also honest in demonstrating some of their weaknesses as well.
For instance, early in the book, Nichols asks a question that he asks all of his students in his classes and offers a chart of the possible ways to see this in a chart on page 12. He explains a potential problem between the Westminster Confession and the Larger Catechism question 31 when we try to distinguish between the essence/substance verses the implementation of God's Covenant of Grace. He quotes the London Baptist Confession 7:2.
...a covenant of grace, wherein he freely offereth unto sinners life and salvation by Jesus Christ, requiring of them faith in him, that they may be saved; and promising to give unto all those that are ordained unto eternal life, his Holy Spirit, to make them willing and able to believe.
To which he then leads his students in a series of questions as to the nature and application of the covenant of grace.
What is the promise? And someone says, life and salvation by Jesus Christ....Now who are the partakers? To whom is this promise made? And now another student says, sinners. Correct. And so I ask, what is the condition? What does God require sinners do to be saved? And the class answers, believe, have faith. It says, "requiring of them faith in Him."
Now follow his train of thought here in his next questions.
Then I ask, are these sinners converted or unconverted?
Of course the class inevitably answers unconverted because of the command that they must believe.
To which he responds:
So then, the partakers are lost sinners indiscriminately, all unconverted persons who hear the Gospel. Thus if this defines the essence of the covenant of grace, then it would be a conditional covenant between God and unconverted sinners.
Now here is where things get a little tricky when he deals with the effectual call.
What is the promise?
To which the students respond.
promising to give unto all those that are ordained unto eternal life, his Holy Spirit, to make them willing and able to believe.
Now who are the partakers? Obviously this would be God's elect. So what does God require of the elect? What does He require them to do?
To which Nichols responds to his students,
Then it's unconditional...So then someone has to admit, the elect are viewed as unconverted, and it says that God promises the unregenerate elect that he will give them his Holy Spirit to make them willing and able to believe....
Now if you see the problem then you have a sharp mind, but if you don't then let me cite Nichols again from page 12.
So now I say to the class, does this define the essence of a covenant between God and His people? Now, not reluctantly, but emphatically, and usually a little shocked, they affirm that it does not.
Nichols uses this approach in order to help the reader understand those whom he surveys. It becomes obvious when Nichols interacts with Hodge and Gill and the others that they also saw this problem in their attempts to provide a sound covenant theology. As he concludes in his chapter, Summary of the Classic Reformed Doctrine,
The general and effectual call should not be regarded as distinct expressions of divine covenant. Rather, God, in His inscrutable wisdom, has determined to fulfill His covenant of grace, His pledge to apply redemption to His elect, through the general ad effectual call of the gospel, not in isolation, but in combination. Thus, it is not the hearers of the gospel who partake in this divine covenant, but the receivers and doers of the gospel, who obey the gospel in repentance and faith.
Therefore we must keep the means and essence of the covenant distinct when seeing how we define the covenant of grace.