\lor {Loves}(x,{Father}(x))$.<br />

    3.  ${\forall\,x\;\;} {Cat}(x) \land ({Loves}(x,{Mother}(x))\lor {Loves}(x,{Father}(x)))$.<br />

2.  Every dog who loves one of its brothers is happy.<br />

    1.  ${\forall\,x\;\;} {Dog}(x) \land (\exists y\ {Brother}(y,x) \land {Loves}(x,y)) {\:\;{\Rightarrow}\:\;}{Happy}(x)$.<br />

    2.  ${\forall\,x,y\;\;} {Dog}(x) \land {Brother}(y,x) \land {Loves}(x,y) {\:\;{\Rightarrow}\:\;}{Happy}(x)$.<br />

    3.  ${\forall\,x\;\;} {Dog}(x) \land [{\forall\,y\;\;} {B