Related Questions

Consider the first-order logic sentence ? ≡ ∃?∃?∃?∀?∀?∀?∀? ?(?, ?, ?, ?, ?, ?, ?) where ?(?, ?, ?, ?, ?, ?, ?) is a quantifier-free first-order logic formula using only predicate symbols, and possibly equality, but no function symbols. Suppose ? has a model with a universe containing 7 elements.