User blog comment:Emlightened/Little Bigeddon/@comment-24061664-20170117003234

I have 2 more questions.


 * I don't quite get the meaning of ∃!a(φ(a))∧φ(k), especially ∃!a.
 * The true predicative is trinary so it appears that unary formula φ can't have true predicative. How expressive is the unary formula in high rank?