The power of positive thinking. It’s like rust on our collective consciousness, an idea that’s seems virtually impossible to eradicate, slowly eating away at our collective psyche. The idea has become so ingrained in our culture that it’s part of our folklore and our idiom, and it continues to be deliberately perpetuated by success coaches, business leaders and others who make a very tidy living by peddling baseless optimism. It’s been repeated so often that the ‘power of positive thinking’ has become an Availability Cascade (a self-reinforcing process by which an idea gains plausibility through repetition).
Herbert and Forman summarise it nicely, “The ideas that thoughts and beliefs lead directly to feelings and behavior, and that to change one’s maladaptive behavior and subjective sense of well-being one must first change one’s cognitions, are central themes of Western folk psychology. We encourage friends to ‘look on the bright side’ of difficult situations in order to improve their distress. We seek to cultivate “positive attitudes” in our children in the belief that this will lead to better academic or athletic performance. Traditional cognitively-oriented models of CBT (e.g., CT, stress inoculation training, and rational emotive behavior therapy) build on these culturally sanctioned ideas by describing causal effects of cognitions on affect and behavior, and by interventions targeting distorted, dysfunctional, or otherwise maladaptive cognitions.” 
Dr Caroline Leaf is a communication pathologist and a self-titled cognitive neuroscientist. She is one of the many that continue to perpetuate the myth of positive and negative thinking.
Today’s social media meme was yet another promotion of this misguided idea, and to top it off, she misquoted scripture again in an attempt to reinforce it.
“If you randomly allow any negative thought into your mind damage can ensue on a mental & physical level. ‘We destroy every proud obstacle that keeps people from knowing God. We capture their rebellious thoughts and teach them to obey Christ.’ 2 Corinthians 10:5 NLT”
Lets quickly break meme down to see exactly why Dr Leaf is, yet again, misleading her audience.
1. The mind does not control the brain
Dr Leaf’s meme implies that negative thought damages us mentally and physically. The problem with that is that the mind doesn’t control our brain or our body, so negative thought can’t damage us mentally or physically.
Instead, it’s our brain that gives rise to, and controls our thoughts and feelings. We don’t see what goes on ‘under the hood’ so to speak, we only experience our thoughts and feelings, so we assume that regulate each other. But it’s our brain and a number of other processes that are responsible for generating both our thoughts and feelings (CAP blog).
‘Negative’ thoughts can sometimes be the result of damage to our brain, but ‘negative’ thoughts don’t damage the brain.
In fact, often the so-called ‘negative’ thoughts are actually good for us.
2. Negative thinking is normal and healthy
Dr Leaf’s meme also implies that we control the content of our thoughts by suggesting that we ‘allow’ negative thoughts into our minds. But negative thoughts are meant to be there, which is why we have them. ‘Negative’ thoughts have a positive function. We need them to survive.
For example, we have a fear response to prevent us from continually putting ourselves in danger. We have an anger response to motivate us through difficult obstacles. We have feelings of embarrassment to help maintain social cohesion. As Skinner and Zimmer-Gembeck state, “adaptive coping does not rely exclusively on positive emotions nor on constant dampening of emotional reactions. In fact, emotions like anger have important adaptive functions, such as readying a person to sweep away an obstacle, as well communicating these intentions to others. Adaptive coping profits from flexible access to a range of genuine emotions as well as the ongoing cooperation of emotions with other components of the action system.” 
Dr Leaf isn’t helping anyone with her meme today. She’s simply promoting an outdated and unscientific notion, encouraging her audience to suppress normal, helpful adaptive functions for fear of harm that’s not scientifically possible.
Then as if to add insult to injury, she follows up her misleading meme with an equally misleading misrepresentation of 2 Corinthians 10:5.
3. Taking every thought captive?
2 Corinthians 10:5 is Pauls famous scripture about taking every thought captive, a concept which seems to support Dr Leaf’s ideas, except that Paul isn’t speaking generally to us, but specifically about the Corinthian church. Look at the verse in context:
“By the humility and gentleness of Christ, I appeal to you – I, Paul, who am ‘timid’ when face to face with you, but ‘bold’ towards you when away! I beg you that when I come I may not have to be as bold as I expect to be towards some people who think that we live by the standards of this world. For though we live in the world, we do not wage war as the world does. The weapons we fight with are not the weapons of the world. On the contrary, they have divine power to demolish strongholds. We demolish arguments and every pretension that sets itself up against the knowledge of God, and we take captive every thought to make it obedient to Christ. And we will be ready to punish every act of disobedience, once your obedience is complete.
You are judging by appearances. If anyone is confident that they belong to Christ, they should consider again that we belong to Christ just as much as they do. So even if I boast somewhat freely about the authority the Lord gave us for building you up rather than tearing you down, I will not be ashamed of it. I do not want to seem to be trying to frighten you with my letters. For some say, ‘His letters are weighty and forceful, but in person he is unimpressive and his speaking amounts to nothing.’ Such people should realise that what we are in our letters when we are absent, we will be in our actions when we are present.” (NIV UK, 2 Corinthians 10:1-11)
This chapter is a specific rebuke to some of the Christians within the church at Corinth, and also a defence against some of the murmurings and accusations that some in that church were levelling at Paul. For example, in verse 2, “I beg you that when I come I may not have to be as bold as I expect to be towards some people who think that we live by the standards of this world.”
Verses 3-6 are a specific and authoritative rebuttal against the accusations levelled at Paul, paraphrased as, “You may speak against us and the church, but we have weapons that smash strongholds, and we’re coming to take down those pretensions of yours and take every thought of yours captive to make it obedient to Christ, and punish every act of disobedience …”
The specific nature of the verse is also supported by some Bible commentary: “But how does St. Paul meet the charge of being carnally minded in his high office? “Though we walk in the flesh [live a corporeal life], we do not war after the flesh,” or “according to the flesh,” the contrast being in the words “in” and “according.” And forthwith he proceeds to show the difference between walking in the flesh and warring according to the flesh. A warrior he is, an open and avowed warrior – a warrior who was to cast down imaginations and every high thing that exalteth itself against the knowledge of God, and bring into captivity every thought to the obedience of Christ; a warrior too who would punish these Judaizers if they continued their disorganizing work; but a prudent and considerate warrior, deferring the avenging blow till “I am assured of your submission” (Stanley) “that I may not confound the innocent with the guilty, the dupes with the deceivers.” What kind of a preacher he was he had shown long before; what kind of an apostle he was among apostles as to independence, self-support, and resignation of official rights in earthly matters, he had also shown; further yet, what kind of a sufferer and martyr he was had been portrayed.” (C. Lipscomb – http://biblehub.com/commentaries/homiletics/2_corinthians/10.htm)
Similarly, the translation from the original text is more specific than general. The verb used for “bringing into captivity” is aichmalōtízō, “to make captive: – lead away captive, bring into captivity” which is in the Present Active Participle form of the verb. The present tense represents a simple statement of fact or reality viewed as occurring in actual time. The active voice represents the subject as the doer or performer of the action. The Greek participle corresponds for the most part to the English participle, reflecting “-ing” or “-ed” being suffixed to the basic verb form. Actions completed but ongoing or commands are different verb tenses (see https://www.blueletterbible.org/help/greekverbs.cfm for a better explanation). So Paul wasn’t making a general statement, but a specific statement about what he would do in his present time, not the future.
So, Paul isn’t telling us to “bring every thought captive into obedience to Christ”. Dr Leaf is perpetuating a common scriptural misunderstanding.
A verse which better clarifies what God wants for our thought life is Paul’s exhortation to the Philippian church in Philippians 4:8, “Finally, brothers and sisters, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable – if anything is excellent or praiseworthy – think about such things.” Both the context, and the form of the verb, suggest that this is an ongoing command. And it makes better sense too. If we spend all of our time trying to fight against every thought that comes into our head, we’d become exhausted, but we can divert attention to those things that are worthy of our attention. And in many ways, what Paul is encouraging is what would be considered now as simple meditation, which is more scientific than the power of positive thinking.
The moral of this story … ‘negative’ thoughts and feelings don’t do us damage, but trying to unnecessarily suppress them does.
 Herbert, J.D. and Forman, E.M., The Evolution of Cognitive Behavior Therapy: The Rise of Psychological Acceptance and Mindfulness, in Acceptance and Mindfulness in Cognitive Behavior Therapy. 2011, John Wiley & Sons, Inc. p. 1-25.
 Skinner EA, Zimmer-Gembeck MJ. The development of coping. Annual review of psychology 2007;58:119-44.