As Christians, we believe that God has revealed Himself in the sixty-six books of the Bible. Any belief about God that does not line up with what has been revealed in the Bible is not the true God. It is an idol. Puritan William Perkins (1558-1602) once put it like this: “God is to be conceived as He reveals Himself unto us” in the Scripture, “and not otherwise; if otherwise, God is not conceived but a fiction or idol of the brain.”
So, when we talk about the “the doctrine of God”—who He is and what He does—it matters. We are not talking merely about abstract theological concepts. We are talking about a true and existent being.
Imagine, for instance, you are accused of a murder. A witness to the murder said the killer was about five feet tall. You are six feet tall. Does it matter that the investigators “get your height right?” You betcha! It’s evidence for your acquittal! Getting God right matters because we are talking about the true and existent God. We do not want to misrepresent him.
Not only is it important to get God right for his sake, it is important to get God right for our sake. When we think and talk about God, it affects literally everything about us. A. W. Tozer has famously said: “What comes into your mind when you think about God is the most important thing about you.” How you think and talk about God determines the quality of your marriage, how you perform your work, what you spend your money on, the principles by which you raise your kids, and a million other practical decisions and actions you make in everyday life.
To be sure, getting God right is a pursuit that will take the rest of our lives. None of us have a perfect doctrine of God because none of us are God! Nevertheless, we still pursue a more accurate knowledge of God. We renew our minds according to the Scriptures, so that we are more and more like Him.
And thankfully, when we get God right, our theology and practice has the potential to line up. Like buttoning a shirt, if you get the first button lined up in the correct hole, chances are the other buttons will line up correctly. But if you get the first button lined up in the wrong hole, none of the buttons will line up correctly. When you get God right, it puts you in place to have your theology and practice line up correctly.
And this is why getting God right matters.
As a start, to help with “getting God right,” listen to the recent message, found here.
 The Works of William Perkins, vol. 7, 421.