diff --git a/README.md b/README.md
index 01b81ec..bc0b91b 100644
--- a/README.md
+++ b/README.md
@@ -43,7 +43,8 @@ In priority order.
    rendered document sees or follows, its text, images and link targets. Content the document only
    references is marked where it stood, by a note that reads as the converter's and names what was
    left out. The lossy pair creates and exports; it never saves back over the document it read —
-   identity (task, mention, media ids) lives only in the lossless pair.
+   a document's identity (task, mention, media ids) survives a round trip only through the lossless
+   pair.
 6. **What happens is what the audience expects.** Where the goals leave a choice, a conversion
    takes the one its audience would predict, reading the input as written.
 7. **Failures are values.** Nothing throws, and `code` is a closed list — as much a contract as