This last point is worth reflecting on in a bit more detail. We ourselves might be tempted to say that since, in the incarnation, the simple divine Word becomes composite, then obviously the incarnation is a case of change: How could going from being simple to being composite not be a change? And yet the very fact that the pre-incarnate Word is simple is, on Aquinas’s way of thinking, sufficient all by itself to rule out the incarnation’s being a mutatio. It is a case of becoming, of course, but not – in Aquinas’s special sense – a case of mutatio.
