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Dawn on someoneのメタフォリカルなイメージ

A dawn on B「AがBに（はじめて・だんだん）わかる」という表現と、このonの意味についてClaude先生にきいてみました。

とね：I wonder what the preposition "on" means in the idiom "dawn on someone". Can you visualize the meaning or image of this expression?

Claude: That "on" is doing the same job it does in "the sun shone on the field" or "the spotlight fell on her" — it marks the surface that light lands on and illuminates.

The verb "dawn" here is a metaphor: understanding is conceptualized as daybreak, and the moment of realization is the moment the "light" of comprehension breaks. Since dawn is fundamentally about light spreading and settling onto a surface (a landscape, a wall, a face), the person who suddenly understands is grammatically cast as that surface. The truth doesn't dawn to you or for you — it dawns on you, the same way sunlight dawns on a hillside.

This puts "dawn on" in a small family of English idioms that use "on" for an idea's sudden, often unbidden arrival at a person, treating the mind as a receiving surface:

• it struck her (impact on a surface)
• the thought came upon him (arrival, landing)
• it occurred to him — interestingly this one uses to, not on, because "occur" frames it as movement toward a goal/recipient rather than light settling on a surface. That's a nice minimal pair: "occur to" (path/goal semantics) vs. "dawn on" (contact/surface semantics).

So the choice of "on" isn't arbitrary collocation to memorize — it's motivated by which physical scene "dawn" evokes. If you swapped in "occur," "on" would sound wrong, and if you swapped in "dawn," "to" would sound wrong, precisely because each verb carries its own embedded image schema.

とね：Thank you so much! Your explanation has "shed light on" the metaphorical image of this idiom and "enlightened" me!

Claude:  Ha — nicely done, and fittingly you reached for two more members of the same metaphor family without even trying. "Shed light on" and "enlighten" both run on the identical understanding-is-illumination mapping as "dawn on," just with different verbs doing the light-casting:

• "shed light on X" — light directed onto a topic (the topic as surface, "on" again)
• "enlighten someone" — literally "put light into" someone (en- + light), so the light goes inside rather than landing on a surface

That's actually a fun contrast with "dawn on": "enlighten" internalizes the light (into the mind), while "dawn on" and "shed light on" keep it external, arriving at or falling upon a surface. Same conceptual metaphor, different spatial construal — which is very on-brand for the kind of pattern you like digging into.

Glad it landed. Always fun working through these with you.

おまけ：ChatGPT先生はつぎのえをかいてくれました。