Is Moral Theology a speculative or practical science?
Moral Theology is not 'one science', i.e., a whole science. It is an integral part of Sacred Theology, which is one, whole science. So the question is whether the science of Sacred Theology is practical or speculative. One can't really ask whether an elephant trunk, elephant legs, or an elephant tail is a quadruped. It only really makes sense to ask whether an elephant is a quadruped.
Now, Aquinas answers this question in the first question of the Summa Theologiae (ST Ia, q. 1, a. 4). His answer may seem slightly strange at first but as you read on in the Summa it starts making more sense: he says that Sacred Theology is both speculative and practical, but that it is primarily speculative. We ought to study it primarily for the sake of knowing God (hence it is speculative, for speculative sciences exist for the sake of knowledge), although it also helps us order our actions toward God (and hence is secondarily practical, for practical sciences exist in order to guide our actions).
But I suppose you could say that moral theology is the practical part par excellence of Sacred Theology, as its whole function is to guide our actions toward God.
So is it accurate to say that doctrines concerning Faith are speculative and hence of the speculative intellect, whereas doctrines concerning Morals are practical and hence of the practical intellect?
Mostly, although in reality the use of both is intertwined in the different parts of Theology. Just to cite two examples, in dogmatic theology we speak of God's providence, which has lots of practical ramifications for our moral and spiritual life, and in moral theology we speak of the passions, which help us understand Christology (dogma) in a speculative way.
Note that the very terms dogmatic and moral theology are not used by St. Thomas. Not only are they posterior to him in origin, but they are somewhat inadequate as they give the impression that there are different 'theologies' or theological sciences. According to him there is only one Sacred Theology (sacra doctrina) and it has parts or treatises that are more or less speculative/practical. The moral part (IIa Pars) is naturally more practical, but there is lots of speculative thought in it, and the predominantly speculative parts (Ia, IIIa) which we now call 'dogmatic theology' have lots of practical applications. Moreover there are treatises, like that on grace and the one the sacraments, which are both specualtive and practical to such equal extents that some scholastic authors disagree as to whether they consider them dogmatic theology or moral theology. (St. Thomas treats of grace in his predominantly practical IIa pars, and of the sacraments in his predominantly speculative IIIa pars, but you can't really blame other authors for thinking that the treatise on grace is speculative or that the treatise on the sacraments is practical.)
One good author to consult here is Garrigou-Lagrange, esp. his introductions to his commentaries on the Summa. He was perfectly faithful to the thought and principles of St. Thomas in a time when many scholastic (and non-scholastic) authors were less consistently Thomistic, at least insofar as they lost sight of some of the nuances of Aquinas' understanding of science and of sacred theology.
Thank you, Doctor. One more question: Is this accurate? "Abortion is morally evil" – speculative intellect (doctrine of Faith). "You shall not commit abortion" – practical intellect (doctrine of Morals).
Both are practical because they both have to do with moral actions. It's not just a question of grammar ('is' vs. 'shall not') but a question of being vs. action ('is the case' vs. 'should be the case'). Something more speculative would be 'abortion is the killing of a fetus', whereas 'abortion is wrong' is practical.
So ‘abortion is the killing of a fetus’ is a doctrine of Faith, whereas ‘abortion is wrong’ is a doctrine of Morals?
Yes, one could say that.
Thank you. I have been struggling with this Faith/speculative vs. Morals/practical distinction for some time. I knew that I could come to you for a clearer understanding. God bless.
You're welcome. I'm glad I could help a bit.