I am considering the Ricardian model.
There is an economy with two countries $S,T$. Two goods $a,b$. Each country has linear production technology with labor ($\ell$) as only factor of production. $$y_i^j=\alpha_i^j\ell$$ where $i \in \lbrace a,b\rbrace$ and $j \in \lbrace S,T \rbrace$.
$$\ell_S + \ell_T = 1$$
The firm's maximization problem is
$$\max_{\lbrace \ell \rbrace} \pi^j_i = \alpha_i^j\ell p_i-w^j \ell$$
There are 3 cases to this problem
Case 1: $p_i^j \alpha_i^j <w^j$
$\ell = 0$
$y_i^j = 0$
Case 2: $p_i^j \alpha_i^j > w^j$
$\ell = 1$
$y_i^j = \alpha_i^j$
Case 3: $p_i^j \alpha_i^j = w^j$
$\ell \in [0,1]$
$y_i^j = [0,\alpha^j_i]$
My Question
Apparently, cases 1 and 2 aren't valid. I'm not sure why. Can someone explain?
The logic is supposed to be
"if there is complete specialization then $\ell_S = 1, \ell_T = 0, y_T = 0$ or $L_S = 0, L_T = 1, y_S = 0$, so therefore cases 1 and cases 2 fail"
I just don't understand this explanation at all and would like a better explanation. What does it mean to "specialize completely"?