I need to think more about this issue of the Trinity and universals – I think nominalism is one reason why there was a turn towards different kinds of unitarianism circa late 1500s through much of the 18th c. (BTW – I’m a nominalist for purely metaphysical reasons.)

What’s disturbing is that on the face of it, some kind of realism about universals is required by patristic (if not creedal) orthodoxy.

Yeah– I suppose if you are a nominalist on the question of universals (of any sort) then some doctrine that says there are three distinct X’s that have the numerically same Y-kind-instantiation is going to be a problem. And this– is more or less what happened in much Trinitarian speculation in the early to middle 14th c. Once Ockham started shaving—theories like those of Aquinas, Henry of Ghent and Duns Scotus appeared less persuasive to crowds of young graduate students (or the equivalent). Though, I hope I’m wrong on this– and that just more historical research will uncover vast fields of Trinitarian speculation hitherto unknown to us/me. I wonder whether Suarez has a place in this history?