A thought terminating cliche commonly-used phrase, sometimes passing as folk wisdom, used to quell cognitive dissonance, especially in cases where the person experiencing the cognitive dissonance might resolve it by reaching a thought-provoking epiphany. For example: John tells his friend Steve, who is considering smoking cannabis, "drugs are bad." Steve takes his friend's advice, and terminates his consideration of smoking cannabis. If he continued to consider his course of action, Steve may have learned that cannabis is good for MS, from which he has suffered for 3 years, but he will never know that because he has fallen victim to a "thought terminating cliche."

The thought-terminating cliché is related to the opaque pigeonhole, or closed category, which does not permit analysis. For examples, flushing the 'nasties' out of aquarium gravel may remove beneficial bacteria too.