A key concept in cognitive behavioural therapy (CBT) is that people may suffer from cognitive distortions—maladaptive patterns of thinking. For example people may jump to conclusions about what someone else is thinking (mind reading) or about the future (fortune telling). Another cognitive distortion is black-and-white thinking—also known as all-or-nothing thinking or dichotomous reasoning—where people see situations in terms of false dilemmas such as “always” or “never”.
Clearly black-and-white thinking can be harmful. It may obliterate nuance, polarize discussions, and preclude compromise. Black-and-white thinking can also go along with absolutism. When arguments get heated, thinking can often become black and white, opinions can become polarized, and positions can harden. Many challenging situations involve shades of gray. Altering the metaphor a little, it has been argued that such situations require full-colour thinking. (Incidentally, the term full colour certainly sounds better than black and white, evoking images of colour photographs and television. But this hardly constitutes an argument in favour of full-colour thinking.) It is often suggested that when we look for solutions, instead of the dichotomy of “either/or” we should focus on the spectrum of possibilities evoked by “both, and”.
And yet, dichotomous thinking is not intrinsically invalid. Some situations are naturally dichotomous. It is not possible to both buy a new car and not buy one. Death is notoriously dichotomous. Other situations may indeed involve a continuum, and yet it may still be useful to consider whether some threshold has been crossed. Consider blood pressure: although it is inherently continuous, when it is high enough doctors get concerned and label it hypertension. In such cases the question is always where the cut-off should be, not whether there should be a cut-off. Dichotomous thinking often involves absolutes, but that is not always a bad thing. When a company bids on a contract, they are either successful or not. A bid may be good, but if it is not accepted then that is irrelevant. Dichotomous thinking has several inherent advantages. First, with binary propositions logic is particularly straightforward. Indeed classical logic focuses on such cases. One of the basic principles of logic is known as the law of the excluded middle which asserts that either a proposition is true or its negation is true. Aristotle expressed it in his principle of non-contradiction, in which he asserted that if you have two contradictory propositions, one must be true and the other false. The application of logic to non-binary situations is far more complex. In the early 20th century, Jan Łukasiewicz and Alfred Tarski developed a “many-valued” logic, a version of which is today known as fuzzy logic. While this has various applications, it is certainly not as straightforward as classical logic. A second advantage of dichotomous thinking is that by focusing on clearly defined situations it has the potential to shed light on a situation. Either I catch the train or I don’t. What should I do if I don’t catch it? Either my grandfather gets admitted to hospital or he doesn’t. If he doesn’t get admitted, what arrangements do I need to make? True, such thinking does not cover all aspects of the situations we face, but it can quickly focus on some crucial issues.
Consider the issue of texting while driving. A black-and-white approach is to simply declare that one should never send text messages while driving. If we’re already wanting to engage in this practice, full-colour thinking might suggest that it is sometimes acceptable to do this (perhaps if we only send short messages). However, evidence shows that texting while driving is exceedingly dangerous. In this case, black-and-white thinking will likely lead to the better decision.
The problem then is not with black-and-white thinking per se, but with its inappropriate use. One way this can happen is when black-and-white thinking becomes a habit. Rather than choosing to apply black-and-white thinking in a selective fashion according to the situation, we apply it reflexively.
One difficulty that arises when we review our patterns of thinking is in the way we often use language. Common expressions can make it sound like we are using black-and-white thinking. For example, “Did you like the movie?”, “Are you happy with your job?” Ordinarily we know to interpret expressions like these in a more nuanced way—”How well did you like the movie?”, “How happy are you with your job?”. It is sometimes suggested that communication can be improved by avoiding black-and-white language. That may be a useful approach, particularly when relations are strained and communication is breaking down. But it would be a mistake to suppose that the patterns and difficulties of communication and thinking reflect one and the same issue.
Black-and-white thinking has been widely criticized—sometimes in a way that can itself be best described as black-and-white. For example, one article, with apparent unawareness of the irony of the situation, promises to help you “Get Rid of Black and White Thinking Once and for All”.
The challenge is not to foreswear black-and-white thinking, but rather to use it appropriately. The best approach may be to flexibly select between black-and-white and full-colour thinking, acknowledging the limitations in both case. Thinking can be distorted by any number of biases, cognitive short-cuts, and fallacies. When there is a lot at stake, one should always scrutinize one’s thought processes and conclusions, and even when no defects are immediately apparent, a degree of humility is called for.