Just what does it mean to “believe”? This doesn’t seem like it would be a tough question (and maybe for some folks it isn’t), but within Protestantism this is a nuanced and long-discussed question. After all, we both believe that salvation is by “faith alone”, which means that we are justified in the sight of God exclusively by our faith in the Gospel. Yet at the same time, we are saved by “grace alone,” which means that salvation comes entirely from outside of us. This would seem to be at odds with the “faith” that needs to be present in us in order for us to be saved. And all this without even mentioning the place of “works” or, to use an Edwardsian idea, “affections.”
This tension is what Piper engages in What is Saving Faith? Reflections on Receiving Christ as a Treasure. Joining a long tradition of theologians, Piper gives us his definition of “saving faith”
“Saving faith is the God-given act of the human heart receiving, as its supreme treasure, Jesus Christ with all that God did for us and is for us in him.” (214)
The book is dedicated to walking through this definition and exploring its implications for various aspects of our lives as believers (including evangelism, assurance, and the Christian life). As with every Piper book, this is thorough in its exploration and thoughtful in its devotional concerns. Piper anticipates objections, including that he is reestablishing a crypto Catholicism and nudging us back towards a works-based righteousness. Piper responds to such potential arguments along the way as he builds his case.
This book is excellent and worth your time. It is a helpful guide for those who want to reflect on what it means to have faith, and a challenge to those who want to float thoughtlessly through the Christian life without serious pursuit of belief in the Gospel.