James, \z.(X(z)->Y(z)) is true when there is no element in our model for which X is true and Y is false. Or the raw statement X->Y is true in our model when Y is true in our model, X is false in our model, or both.
James, \z.(X(z)->Y(z)) is true when there is no element in our model for which X is true and Y is false. Or the raw statement X->Y is true in our model when Y is true in our model, X is false in our model, or both.