Makowsky and Shelah introduce a logic $L^{\text {pos }}$
- The usual formation rules for $\neg, \wedge, \exists x, \forall x$
- if $\varphi\left(s_{+}\right)$ is a formula of $L^{\text {pos }}$ in which $s$ occurs positively, then $\exists s \varphi\left(s_{+}\right)$ is a formula of $L^{\text {pos }}$.
- if $\varphi\left(s_{-}\right)$ is a formula in which $s$ occurs negatively then $\forall s \varphi\left(s_{-}\right)$ is a formula.
The semantics is given by $\mathfrak{M} \vDash \exists s \varphi(s)$ if there is a countable set $s$ such that $\mathfrak{M} \vDash \varphi(s)$.
# Relations
- properly containing $L(Q)$ [[Generalized logics#Generalized quantifiers]]
- properly contained in [[Stationary logic]]