diff --git a/README.md b/README.md
index d69df67..f5d3ab3 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,8 @@ In priority order.
    document and returns a whole result.
 9. **Fast once correct.** Conversion time grows linearly with the document wherever the goals above
    allow it; a faster path that risks one of them is not taken.
+10. **Source a contributor can hold.** Any one function reads at a sitting, and the gate stops the
+   source drifting longer.
 
 ## Audience