The strength of a theory is not what it allows, but what it prohibits; if you can invent an equally persuasive explanation for any outcome, you have zero knowledge.
They crossed the boundary from Christmas Eve to Christmas Day within that timeless void where Earthly rotations meant nothing, the one true everlasting Silent Night.
Above all, don’t ask what to believe – ask what to anticipate. Every question of belief should flow from a question of anticipation, and that question of anticipation should be the center of the inquiry.
Harry had run into trouble falling asleep Friday night, which he had anticipated might happen, and so he had decided to take the obvious advance precaution of buying a sleeping potion; and to prevent it from constituting a visible sign that he was nervous, he had decided to buy it off Fred and George a couple of months earlier.
Well, sounding wise wasn’t difficult. It was a lot easier than being intelligent, actually, since you didn’t have to say anything surprising or come up with any new insights. You just let your brain’s pattern-matching software complete the cliche, using whatever Deep Wisdom you’d stored previously.
She was taken to St. Mungo’s, where,” the Headmistress now sounded slightly perturbed, “a standard diagnostic Charm showed Miss Granger as a healthy unicorn in excellent physical condition except that her mane needs combing.
If what you believe doesn’t depend om what you see, you’ve been blinded as effectively as by poking out your eyeballs.
You cannot obtain more truth for a fixed proposition by arguing it. To improve our beliefs, we must necessarily change our beliefs.
The truly important problems are often the ones you’re not even considering, because they appear to be impossible, or, um, actually difficult, or worst of all, not clear how to solve.
For it is a sad rule that whenever you are most in need of your art as a rationalist, that is when you are most likely to forget it.
Not every change is an improvement, but every improvement is necessarily a change.
Every improvement is a change, but not every change is an improvement. Every rationalist doubts, but not all doubts are rational. Wearing doubts doesn’t make you a rationalist any more than wearing a white medical lab coat makes you a doctor.
Are you familiar with the economic concept of ‘replacement value’? Hermione’s replacement value is infinite! There’s nowhere else I can go to buy another one!
A playground is a great place to be a bully, and a terrible place to be a victim, if the teachers don’t care who started it.
Never give anyone wise advice unless you know exactly what you’re both talking about.
There are forty kinds of lunacy but only one kind of common sense.
Evil happens, thought Harry, it doesn’t mean anything or teach us anything, except to not be evil.
What I am trying to say is that more than your own life has to be at stake, before a person becomes desperate enough to resort to math.
No rescuer hath the rescuer, Godric Gryffindor had written. No Lord hath the champion, no mother and no father, only nothingness above.
Usually, when things suck, it’s because they suck in a way that’s a Nash equilibrium.
It’s not paranoia if they really are out to get you,” Harry recited the proverb.