t, your quantification theory is first-order).
&gt;
&gt; MW: As I'm sure you know, this is beyond my knowledge. If I assume
&gt; that a quantification theory that is higher order implies a logic that
&gt; is higher order, then my position is as follows. I believe (because
&gt; people like you tell me) that there are significant advantages to
&gt; staying first order.

Or close to it.  There is a proposal before the KIF WG that provides a
semantics for sequence variables that gives KIF a bit more expressive
