A cache is a location where a given piece of information is stored in computer memory. Most of our mental capacity has to come from cached information in the brain. The effort of coming up with new ideas is immense and as a result most of the thoughts in your head aren't entirely yours. This is good, if we each had to independently invent the wheel we'd never get past the level of basic agriculture. But this does leave us open to picking up weird junk ideas that don't have much correlation with reality.
The concept of a cached thought originates from this blog post. In practice a cached thought refers to an idea that enters the mind without being subjected to any real scrutiny despite the source being less than fully trust worthy. We've all heard the claim that people only use ten percent of their brain's capacity and any neurologist will tell you that it's absurd and we've known it's absurd for decades. How about the notion of reason and emotion being at odds. Yes, they don't always get along but Feynman is what a rational person looks like, not Spock.
To use an example from my own life I saw a Facebook post about how someone couldn't understand how an empire like Rome could fall despite having so many technological and resource advantages. I pointed out that Rome's mistake was to hire and arm Germanic tribes and then fail to pay them. Another friend replied that that sound like 'Merica to him. In what conceivable world does America get invaded? We have nukes, we have millions of tons of military hardware, we staff our own armies. The comparison made no sense. And then I remembered that I'd grown up hearing comparisons between the decline of values in the USA and Rome for most of my life. Maybe he had more nuanced reasoning than that and didn't bother explaining it but it stuck with me. Recognizing cached thoughts in one's self and others is one of most effective forms of mental floss that I know of but it's hard because if you've cached a thought that means you thought it was true. Learning to recognize when some part of your web of knowledge is not supported by the rest requires real thought and effort but it's worth it.
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