You don’t have to read very far into The Imitation of Christ before getting a contrast between speculative and practical theology.
“What will it avail thee to dispute profoundly of the Trinity, if thou be void of Humility, and art thereby displeasing to the Trinity? High Words surely make a Man neither holy nor just, but a virtuous Life maketh him dear to God.”
It has to be remembered that speculative theology exists for the sake of practical theology, without which speculative theology is glorious but unfruitful in its splendor, like the sun blazing down on a desert. On the other hand, it will not do to forget that there is no way to account for (to judge, to establish, to correct, to explain and therefore understand) practical theology without speculative theology. Without speculative theology you get a swamp, and everything grows there. You can’t let go of either.
It seems to me that in our idea of the Christian life we favor one or the other, speculative or practical. Thomas à Kempis, for example, is a product of the Via Moderna. This was a medieval phenomenon, one of the by-products of Nominalism, consciously so, and therefore called modern: the modern way. The emphasis was on the use of theology, not its elaboration. Were the elaborations of speculative theology for him not as real? High Words, he said. So I manifest a reservation.
What is funny is that Erasmus, who’s excellent early schooling was with the Brethren of the Common Life (the Via Moderna’s lay manifestation), appreciated this attitude and at the same time embraced the Platonism of Humanism. Both of them, he found, were congenial for doctrinal minimalism. Erasmus was the admired scholar, the father of reasonable men, men of latitude, men of elegance, and men of selective scruples. Luther, a Nominalist by conviction, was the one who saw the profound individual, personal need for a clear articulation of forensic justification. The difference is integrity, and integrity rejoices in the truth, It even makes good use of bad philosophy, it seems.
You can do two things with à Kempis’s emphasis. You can use it to dismiss elaboration, to set aside speculative theology as relatively unimportant. I have not read à Kempis carefully enough recently enough to judge. As you probably can tell, being positive of the Via Moderna is not something I’m keen on. I do understand one must not dismiss all things, even Nominalism and its theological spawn Voluntarism have served good purposes . . . as the sons of Jacob did when they sold their brother to the Ishmaelites on the day of their greatest infamy. Platonism, as can be seen above—a kind of, at least—has served bad purposes. But you can use à Kempis’s emphasis to do a second thing: to make sure speculative theology is being applied.
What I am sure of is this: you cannot drive a wedge between speculative and practical theology. They must be related. They have to be coordinated. The complex relationship should be clear to us, explicit. And we should beware of those who do not value both.