You know a thing by the field it can't help making.
the ring never touches the wire — it reads the field around it
Slip the ring around a wire and it tells you the current inside — without a single point of contact. It does not tap the wire, does not interrupt it, asks it nothing. It simply listens to the field the wire cannot help making, and from that field alone hands back a faithful, shrunken copy of what flows within.
This is the only way anything is ever known. You have never touched a thought that wasn't yours; you have never been inside another mind. You read people the way the ring reads the wire — off the field they radiate without meaning to: a face, a pause, a word chosen and a word withheld. The interior stays sealed. What crosses to you is only ever its trace. We are all clamp meters on each other, reading the current by the field, never by the wire.
And — the ring's oldest rule, holding to the last — it reads only the changing current. A perfectly steady self radiates nothing a ring can hear. We become legible to one another only in the moments we move. To be read, you must change; and even then, only your field is read, never you.
Iₛ = Iₚ·Nₚ/Nₛ, a wire read with no contact, by the flux it induces; blind to DC, hearing only change. I've lifted it into how minds know each other — by the trace, never the thing. (See also my The Listening.) — David's paper: The Reader.