看得穿、看得清
這一組最貼近原本的水晶畫面，講的都是眼睛這一端：東西乾淨到視線可以直接過去。
adjective · C1
So clean, and so free from dirt, cloud or anything floating in it, that you can see straight through it or see a long way.
清澈透明
核心畫面
One way to hold this phrase: picture a piece of clean crystal, or a glass of still water. There is nothing inside it and nothing on it, so light goes straight through and whatever is on the far side arrives whole. English keeps that picture and moves it from place to place. Move it to a screen and every small detail survives the trip to your eye. Move it to a phone line and every word survives the trip to your ear. Move it to what somebody says and there is nothing in the way of the meaning either, so only one reading is left.
這個說法的畫面可以想成一塊乾淨的水晶，或是一杯靜止的水。裡面沒有雜質，表面也沒有髒污，光線直直穿過去，另一頭的東西就…更多收起
這個說法的畫面可以想成一塊乾淨的水晶，或是一杯靜止的水。裡面沒有雜質，表面也沒有髒污，光線直直穿過去，另一頭的東西就完整地送到你眼前。英文一直用同一個畫面，只是換位置。換到螢幕上，細節完整送到眼睛。換到電話裡，每個字完整送到耳朵。換到一句話上，意思中間也沒有東西擋住，所以只剩下一種讀法。四個用法其實都在講同一件事：中間沒有東西擋。From the word’s history
The supplied Wiktionary entry traces the phrase to Middle English cristal cleer and calls it an emphatic form of clear, used both of what you can see through and of what you can understand. That fits the core image directly: crystal is named because it is the standard for letting light through, and the phrase borrows that standard for everything else.
封包裡的 Wiktionary 資料說這個說法可以追到中古英語的 cristal cleer，是 clear 的加強版，一開始就同時用在「看得穿」和「聽得懂」兩邊。這正好對上核心畫面：水晶被拿來當「清」的標準，後面所有用法都是借用同一個標準。
Wiktionary entry supplied in this packet (source_ref kaikki:3f6f69a190036ae4:1411491524:19631)
Two branches
聽得清、想得通
同一個畫面換了通道：擋住的東西從眼前搬到耳朵裡，再搬到腦袋裡，判斷的標準還是「中間有沒有東西擋」。
adjective · C1
Used of a sound or a voice that is so easy to hear that every word or note comes through, with no noise, crackle or blur over it.
聲音清晰