Good Works and Final Salvation

It was interesting to find this quote from Peter van Mastricht (1630-1706) about three periods of justification. Mark Jones quotes this with approval in the chapter "Good Words and Rewards" in his excellent book Antinomianism. I have removed Scripture references.

From this come three periods of justification that should be diligently observed here, namely 1: The period of establishment, by which man is first justified: in this occasion not only is efficacy of works excluded for acquiring justification, but so is the very presence of these works in so far as God justifies the sinner and the wicked. 2: The period of continuation: in this occasion, although no efficacy of good works is granted for justification, the presence of these same works, nevertheless, is required. And it is probably in this sense that James denies that we are justified by faith along but he requires works in addition. And lastly 3: The period of consummation in which the right unto eternal life, granted under the first period and continued under the second, is advanced even to the possession of eternal life: in this occasion not only is the presence of good works required, but also, in a certain sense, their efficacy, in so far as God, whose law we attain just now through the merit alone of Christ, does not want to grant possession of eternal life, unless [it is] beyond faith with good works previously performed. We received once before the right unto eternal life through the merit of Christ alone.  But God does not want to grant possession  of eternal life, unless there are, next to faith, also good works which precede this possession. 

Mark Jones closes the paragraph with this note.

It is a sign of the times that not a few in the broadly Reformed church today--indeed, even professors of theology, would have a real problem with Van Mastricht's conclusion that eternal life is not granted unless good works are performed by the godly.

Do we believe that good works are necessary for final salvation? I have found very few Christians, even reformed ones, who would say yes.  Jones' book challenged me on this issue.