Whether it is possible to make ON CONFLICT without unique on the field?

Question

PostgreSQL

INSERT INTO distributors (did, dname)
    VALUES (5, 'Gizmo Transglobal'), (6, 'Associated Computing, Inc')
    ON CONFLICT (did) DO UPDATE SET dname = EXCLUDED.dname;

Onconflict only works if the table has a unique on the columns that are being transferred. Is it possible to make such a request without setting the unique on the fields?

Answer 1

What then is the conflict?