The Welfare Theorems

Define $Y=\sum_mY_m$.

The private ownership economy $\mathcal{E}$ has an optimum if
  1. for all $n$, $X_n$ is closed and bounded from below and $\omega_n\in X_n$,
  2. each $Y_m$ is closed, convex, and contains 0,
  3. $Y\cap\R^L_+=\{0\}$ and $Y\cap -Y=\{0\}$,
  4. for every $x'_n\in X_n$, the set $\{x_n\in X_n:x_n\succeq x'_n\}$ is closed.