Full Idea
Kripke showed via a fixed-point argument that certain three-valued languages can contain their own truth predicates.
Clarification
A fixed point occurs when a function outputs its input value
Gist of Idea
Certain three-valued languages can contain their own truth predicates
Source
report of Saul A. Kripke (Outline of a Theory of Truth [1975]) by Anil Gupta - Truth
Book Reference
'Blackwell Guide to Philosophical Logic', ed/tr. Goble,Lou [Blackwell 2001], p.94
A Reaction
[Gupta also cites Martin and Woodruff 1975] It is an odd paradox that truth can only be included if one adds a truth-value of 'neither true nor false'. The proposed three-valued system is 'strong Kleene logic'.