We are often more certain than the evidence really allows.
More quotes“How well do you understand how a toilet flushes?”
“Eight out of ten.”
“Explain it.”
“You press the handle and water comes into the bowl.”
“From where?”
“The cistern.”
“What releases it?”
“The handle opens something.”
“What?”
“A valve.”
“Draw it.”
A rectangle appears. A line connects the handle to a circle.
“What is the circle?”
“The valve, probably.”
“What closes it?”
“The water level.”
“How does water level move the valve?”
“The float.”
“Where is the float?”
Another circle appears.
“What connects it?”
A line is drawn, erased and drawn again.
“What lets new water enter?”
“A separate valve.”
“What opens that?”
“The float, I think.”
“Is that the same float?”
“Maybe.”
“What makes the bowl water leave?”
“Pressure.”
“From which water?”
“The cistern water.”
“Where does it go after the bowl?”
“Into the pipe.”
“What stops gas coming back?”
“The bend.”
The confidence rating changes from eight to five.
“Which part are you least sure about?”
“The connection between the handle and the flush valve. And whether I’ve mixed up two valves.”
The page now contains two rectangles, three circles, one U-shaped pipe and a line ending in blank space.
“What would you look up first?”
The pencil points to the unfinished line.