Anchor: But this is an artifice, and it is not foolproof.
Entailed: Not only is it not perfectly sound, it is also merely a clever device.
Contradiction: It is so perfect it can't fail.
Contradiction: He was completely honest and told the truth. 
Contradiction: He is a current writer for our Webhead column, and will remain in his position for the foreseeable future.
Contradiction: The boy is asleep.
Contradiction: yes that's another system I use, I'm internally linked to Texas Instruments in Attleboro