Here’s a great Q&A from John MacArthur’s book on Biblical Counseling (emphasis is mine):
Since the Bible is not a textbook on psychology, don’t we need to supplement it with other disciplines to understand and help people with deep psychological needs?
At first glance, this seems like a reasonable question. The scientific disciplines have shown us truth that goes beyond the truth of Scripture. All of us have benefited from medical knowledge that is, after all, extrabiblical. Appendectomies, for example, have saved countless lives in the past hundred years or so. Smallpox vaccinations have virtually wiped out the disease. If we limited ourselves in medicine to the remedies specifically revealed in Scripture, we would be at a tremendous disadvantage in the treatment of diseases.
Certainly, Scripture does not claim to be a thorough textbook on medicine, or physics, or any of the sciences.?3? But psychology differs from these in two important regards. First, psychology is not a true science. It does not deal with objective, measurable data that can be subjected to reliable tests and confirmed by the scientific method. It is a pseudoscience, and most of its cardinal doctrines are mere speculations, not reliable truth.
Second, and most significant, psychology, unlike medicine and physics, deals with matters that are fundamentally spiritual. In fact, the word psychology literally means, “study of the soul.” What are deep psychological needs if they are not the spiritual issues the gospel is concerned with? And Scripture certainly does claim absolute sufficiency in addressing those needs: “All Scripture is inspired by God and profitable for teaching, for reproof, for correction, for training in righteousness; that the man of God may be adequate, equipped for every good work” (2 Tim. 3:16–17, emphasis added). “The law of the LORD is perfect, restoring the soul” (Ps. 19:7). Scripture itself promises believers the most comprehensive spiritual resources: “everything pertaining to life and godliness” (2 Pet. 1:3).
Is the problem depression? Scripture contains the only reliable remedy. Is the problem guilt? What can psychology offer that goes beyond the perfect solution Scripture suggests: ‘’the blood of Christ … [that cleanses] your conscience from dead works to serve the living God” (Heb. 9:14)? Every so-called psychological need that is not traceable to physical causes is, in reality, a spiritual problem, and Scripture does indeed claim to be the only sufficient guide in handling spiritual problems. To attempt to add psychological theory to the unfailing testimony of God’s Word is to adulterate God’s truth with human opinion.
– John F. MacArthur, Jr., MacArthur Pastor’s Library on Counseling, 249-50 (Nashville, TN: Thomas Nelson Publishers, 2005).