I have tendencies. Put me near a Subway restaurant, where I can smell the fresh bread, and I’ll get hungry, my mouth watering. Force me to watch reality TV shows, and I’ll become fatally bored. I have a tendency to smile in the presence of cute little kids.
Doctrines do not have tendencies. They don’t do anything. They have meanings, and they stand in logical relations to other claims. But they have never yet rotted, drooled, fallen off the table, bonked anyone in the shins, or become restless.
So it’s confused to say, for example, that famous theologian Sheppy’s doctrine of the Trinity “has modalistic tendencies”. No, his doctrine – not his words, but the assertions he makes using those words – just is what it is. It doesn’t change, develop, or do anything at all. It doesn’t wake up cranky and heretical on some mornings, well-rested and orthodox on other days.
The only thing that can have modalistic tendencies is Sheppy. He may indeed sometimes think and talk like a modalist.
There is a truth nearby – the content of Sheppy’s doctrine may be vague. He may sometimes use words without precise meaning, words which may lead some readers to think he’s a modalist. It may be, though, that he is simply confused. Perhaps if the confusion is bad enough, we ought to discard his writings, rather than analyze their “tendencies”.