  But the entry for Sω(X) can be either t or f. In other words, the initial hypothesis h0 generates at least two revision sequences. Every revision sequence S that has h0 as its initial hypothesis must have Sω(A) = t, Sω(B) = t, and Sω(C) = f. But there is some revision sequence S, with h0 as its initial hypothesis, and with Sω(X) = t; and there is some revision sequence S′, with h0 as its initial hypothesis, and with Sω′(X) = f. □