“Syncretism” is “the combination of different forms of belief or practice.” It’s one of Satan’s most deceptive and appealing techniques, devised to destroy true faith and undermine the Christian’s confidence in God’s Word and dependence on Christ. Psychotherapy and its underlying psychologies are actually religious in nature and practice. They’re like oil and water! The euphemism for this kind of syncretism is “integration,” which occurs when two or more ideas or systems are combined. However, psychotherapeutic beliefs cannot truly be integrated with Scripture. One works with the old man of the flesh (carnal); the other works with the new man in Christ (spiritual). They’re at enmity with each other, just as the flesh and the Spirit are contrary to each other (Gal:5:17) and just as the carnal man is at enmity with God (Rom:8:7). They can’t mix, because they’re enemies just as the idols of the nations around Israel were at enmity with God.
Christians who mix psychology and the Bible aren’t practicing and promoting ordinary integration but rather religious syncretism, overlaying their psychology with the Bible. This ultimately disguises the psychological religious systems they’re using, and then this psycho-syncretism subverts and subtracts from the faith. The “integrating” of psychology and Christianity appeals to those Christians who believe that what is being discovered about the mind, the will, and the emotions is science—that it’s part of God’s creation yet to be discovered in the same way that discoveries have been made in physics, chemistry, and biology. Since psychology misrepresents itself as a science, and psychotherapeutic ideas are organized into theories, many pastors don’t even realize that these scientific-sounding theories are simply another competing belief system.
Instead of knowledge being added to knowledge with more recent discoveries resting on a body of solid information, in this case, one system contradicts another, one set of opinions is exchanged for another, and one set of techniques replaces another. Psychotherapy changes along with current cultural trends. Just the knowledge that there is an accumulation of about 500 separate psychotherapeutic systems, each claiming superiority, should discourage anyone from thinking that so many diverse opinions could be scientific or even factual. Psychotherapy and its underlying psychologies are amassed in confusion, with their pseudoknowledge and pseudotheories resulting in pseudoscience."
Dr. Martin and Deidre Bobgan and T.A. McMahon, PSYCHOLOGY AND PSYCHOTHERAPY (PART 1).