Bad theology undermines our comfort, assurance, peace, and joy in Christ. Bad theology leads to dark places. Wrong thinking and wrongdoing alike can destroy our lives or at least diminish our intimacy with God and our faithfulness. God intends our thinking to align with His Word, and from it our feeling and doing as well. Obedience to God is the fruit of the Spirit through faith, so it is very important what we believe. Some professing Christians think, “The Bible alone is my theology,” and in one sense that’s true, but what does the Bible mean? And the moment anyone begins to explain what the Bible means, they are expressing some theological framework. But is their framework a good one?
1 Timothy 1:8–11 are thought-provoking verses. Paul lists various sins including murder, sexual immorality, homosexuality, and lying,and adds, “and whatever else is contrary to sound doctrine.” Think about that. Sin is contrary to sound doctrine. The choices we make and the things we do cannot be detached from our doctrine. When we sin, we are not thinking clearly about God. We are actually acting out bad doctrine and discernment. It is also true that when we have bad doctrine, it will inevitably manifest in some type of bad living.
Every two years, Ligonier Ministry and LifeWay Research team up to do a State of Theology survey.  This survey reveals doctrinal trends of Americans in general, but also Evangelical Christians in America, and every year there are considerably troubling results. For Evangelical Christians in 2020:
- 30% believe Jesus was a good teacher, but he is not God.
- 44% reject the idea that God chose the people he would save before he created the world.
- 35% reject the idea that the Holy Spirit gives a spiritual new birth or new life before a person has faith in Jesus Christ.
- 46% believe everyone sins a little, but most people are good by nature.
- 42% believe God accepts the worship of all religions, including Christianity, Judaism, and Islam.
There are many very confused professing Christians sitting in pews all across America, and their bad theology is damaging their lives and greatly destabilizing their comfort, assurance, peace, and joy in the gospel.
There are various reasons why many Evangelical Christians have unsound doctrine and discernment, but I think one of them is they spend time reading the latest and most popular Christian books and blogs, and they fill their minds with unsound theology and old heresies repackaged and follow the current of contemporary culture. Of course, there are wonderful new books and blogs, but many Christians don’t realize that many popular books and blogs derive from historically bad theological frameworks, frameworks that subtly work to undermine their confidence in God and His Word.
How can we guard against this? How can we ensure that our doctrine and discernment are healthy? One great way is to read old theological works, works that Christians have believed for centuries, works that are time-tested. What I mean is, don’t read and study alone. Instead, read and study with the Church of ages past. It should matter to you what Christians have believed and written centuries before you. And as soon as some of you hear that, you may get overwhelmed. Who has time to read centuries of theologians and to discern what is good and bad from each of them? Few of us.
So, as a housewife, plumber, or salesman, how can we grow healthier in our doctrine and discernment? Where would one begin to build a solid doctrinal framework? And the answer is simple. But with the noise of social media and Christian marketing, it is also simple to disregard. It’s not a sexy or flashy answer, but it is an answer that will help you tremendously and not overwhelm you. Baby steps, right? The answer begins with good counsel from Martin Luther. Luther said:
The number of theological books should . . . be reduced, and a selection should be made of the best of them; for many books do not make men learned, nor does much reading. But reading something good, and reading it frequently, however little it may be, is the practice that makes men learned in the Scripture and makes them pious besides. 
That is a profound and helpful statement. Luther recognized that the Bible is the primary source text – so please read your Bible – but he also believed in reading a few good theology books. But where do you start to build a solid theological framework which helps you understand what the Bible teaches? Many Evangelical Christians are not conscious of their theological framework (they do have one), nor are they aware that it’s not a good framework, so they’re all over the place in what they believe the Bible says. They are prime examples of Ephesians 4:14. Additionally, many good theology books are fat and intimidating.
Here’s what I recommend you do. I think you’ll be surprised at how beneficial this will be in your life. Make yourself familiar with the historic Reformed confessions and catechisms. Start with the Heidelberg Catechism. It is clear, concise, simple, and one of the most helpful theological works ever written. It will teach you how to hear and understand the Bible, and it will instill in you a sound doctrinal framework.
You may also want to spend time in some other clear and concise theological works which address other important doctrinal points. Go to the Belgic Confession. Dig into the Westminster Confession of Faith and Westminster Shorter Catechism. There are others, but these few are the place to start. Start working through them at a pace that works for you. When you come to something challenging, discuss it with your elders who love you.
Many Evangelical Christians have anemic doctrine and discernment. There are plenty of reasons for that. But if you take Luther’s advice and dig deeply into one or two good historic Christian confessions or catechisms, you will develop much healthier doctrine and discernment which will fuel your intimacy with God and holiness, as well as boost your comfort, assurance, peace, and joy in Christ. Oh, and make sure you’re in a good church where you hear this kind of substantial theology from the pulpit and get much encouragement from godly shepherds.
 Taken from 21 Servants of Sovereign Joy by John Piper, © 2018, p. 80. Used by permission of Crossway, a publishing ministry of Good News Publishers, Wheaton, IL 60187, www.crossway.org.