Nullius in verba is our motto here. In Latin, it roughly means “take no one’s word for it”.
When people hear that phrase, a common argument that pops up against it is that you sometimes have to take someone’s word for it. You can’t personally recreate the whole of human knowledge now, can you?
There’s a few misconceptions in that argument because you actually DON’T have to “personally recreate the whole of human knowledge” to not take someone’s word for it.
You have to learn the whole of human knowledge to understand everything that can be understood.
You don’t! You don’t have to memorize and know every single fact to fundamentally understand everything that can be understood. Facts can be looked up. And predictions derived. If you understand the deep underlying theories behind everything, then you know at a high level how everything works. And this can all be understood by a single person.
As new theories succeed old ones, our knowledge becomes deeper as our fundamental theories become more general. Our deepest explanations and theories are becoming so integrated with one another that they can be understood only jointly.
We can have explanations that can reach the entire universe.
Note: this doesn’t mean one doesn’t need people. In his famous essay, “I, Pencil”, Leonard E. Reed argues that no one person—repeat, no one, no matter how smart—could create from scratch a small, everyday pencil. People’s minds are a bank of knowledge. We need access to them to solve more problems and for the act of creation to occur. Rather, even to create the most mundane of items such as a pencil. People are better working together, best if they do without any constraints on their thinking.
Seeking and understanding good explanations = taking someone’s word for it
This is a big one. If a person is trying to understand something by asking some “expert” a doubt, this (confused) way of thinking concludes that person is taking the expert’s word for it.
That person is seeking an explanation. Not blindly taking the expert authority’s word for it. If the explanation is not satisfactory (i.e. not hard to vary) then that person will not take the expert’s statement into account. At least the rational person won’t.
For example: If the “expert” says, “To sleep well at night, switch on a strong white light that flashes right onto your closed eyes”… The person seeking good explanations will ask, “How will that affect my sleep in a positive way?”
That person wouldn’t blindly take the expert’s word for it.
Similarly, if a person who seeks good explanations asks a sleep expert: “How can I get better sleep?” and the expert answers: “Make sure not to expose yourself to any sort of blue light that would be flowing out of your digital devices 2 hours before bed. At night time, choose to switch on some calming red light while you perhaps do some physical book reading. Blue light suppresses the secretion of melatonin, a hormone that makes you sleepy. Artificial blue light makes your human brain think its morning, not shut-eye time. So it stops producing a lot of melatonin. A hormone that’s produced more of in darkness. All kinds of light suppress melatonin production but especially blue light. Red or dim yellow light does so the least and can actually be soothing while getting ready for bed.”
This answer would be taken satisfactorily by the seeker of good explanations. Perhaps the person might also ask for some research studies on the point. And this completely wouldn’t be taking anyone’s word for it. It would be understanding a good explanation behind why you shouldn’t expose your eyes to blue light before bed. 
Seeking and understanding good explanations ≠ taking someone’s word for it
Following someone’s instincts and intuitions = taking someone’s word for it
Now the critic might think, OK fine, but at urgent times when you have to listen to someone, that’s taking someone’s word for it. Like if you’re on a plane with Maverick from Top Gun and something goes wrong—and let’s assume you are a complete doofus when it comes to planes—and Maverick shouts at you to pull up a lever, you don’t question him but pull that lever!
You’re supposedly taking his word for it by trusting his instincts.
But are you really? That choice to pull up the lever too is somewhat independent thinking. The person you’re with knows what he’s doing. Or rather you know or you suppose he knows what he’s doing in the literal split second time you have to think. You know that you’re dumb when it comes to planes and if you don’t follow Maverick’s orders you both might die.
Perhaps when Maverick tells you to pull the lever and as if it weren’t obvious enough, you ask him “Why?!” and he screams back, “We’ll both die if you don’t!” that should be enough if you a priori know that Maverick knows his stuff when it comes to planes and that you’re both in quite a lot of danger so following his orders seems to be the rational thing to do.
So when are you actually taking someone’s word for it?
Now it might seem like: OK, so when is someone actually taking someone’s word for it?
There are many instances of when people take someone’s word for it.
- When they don’t seek good explanations and be satisfied with arguments from authority
- When they mistake “it is written” as a justified explanation
- When they mistake supposed intuition for explanation
- When “trust” supersedes the need for a good explanation
- When anything is out of bounds and accepted (perhaps obligatorily) as unquestionable
It’s the (completely different) ways in which people don’t take someone’s word for it, by…
- seeking good explanations,
- understanding deep underlying theories,
- accounting trust for a good enough explanation
that removes the need for taking someone’s word for it.
And so stands tall our motto:
Nullius in verba
 – This wasn’t an example of a direct explanation. Rather some advice built from a good explanation about human sleep. This was due to the nature of the question: “How can I get better sleep?”
- The Fabric of Reality by David Deutsch