boolean states

Hi

http://www.postgresql.org/docs/current/static/datatype-boolean.html states:

The boolean type can have one of only two states: "true" or
"false". A third state, "unknown", is represented by the SQL null value.

This sounds like an oxymoron to me. Perhaps that sentence should be
changed to:

The boolean type can have one of three states: "true" or
"false" and "unknown". The third state, "unknown", is represented by the
SQL null value.
or:

The boolean type can have one of three states: "true" or
"false" and null. The third state, null, represents the logical value
"unknown".

Best regards
Jack Douglas