Abstract:
We study into the question of which linearly ordered sets are intrinsically enumerable. In particular, it is proved that every countable ordinal lacks this property. To do this, we state a criterion for hereditarily finite admissible sets being existentially equivalent, which is interesting in its own right. Previously, Yu. L. Ershov presented the criterion for elements $h_0$, $h_1$ in $HF(\mathfrak M)$ to realize a same type as applied to suficiently saturated models $\mathfrak M$. Incidentally, that criterion fits with every model $\mathfrak M$ on the condition that we limit ourselves to 1-types.