Capture5

type t
relation p(X:t)

axiom [foo] {
    individual x:t
    individual y:t
    property p(x)
    property p(y)
}

theorem [bar] {
    individual x:t
    individual y:t
    property p(y)
    property p(x)
}
proof
    apply foo with y = x, x = y;
    showgoals