  More formally, let A0 be the sentence  Tα0  ∨  ¬Tα0,  and for each n ≥ 0, let An+1  be the sentence  Tαn. Thus  A1 is the sentence  Tα0, and  A2 is the sentence  Tα1, and  A3 is the sentence  Tα2, and so on. Our  ground model M =  &lt;D, I &gt; is as follows: