Theology is a speculative science. Yet this word-- "speculate"-- is used like a slur. Those who use it so really haven't the faintest idea. Theological speculation is when known facts (in the context, dogma and doctrine) are examined so as to reveal what suggestions or implications are included in them, or necessarily follow from them. That's what this expression-- "speculative theology"-- means. St. Thomas' negative proofs are an example of speculative theology. He looked at certain known facts about what God isn't, and from there he arrived at certain conclusions about what God is. There's nothing in any solemn definition that will tell you that God is perfectly simple, or that He is pure act, First Mover, etc. Here are some other examples of speculative theology: That Saint Joseph was only ever married to the Virgin Mary. That Christ had no siblings. That angels are not material in nature. That guardian angels exist. That original sin is passed through the seminal power from the man to his children. That Limbo of the Infants is not a "third eternity," but a part of Hell bereft of any positive punishment, though separated from God forever. That God's efficacious grace can be distinguished from his sufficient grace. That all of the apostles are saints, despite none having ever been solemnly declared to be. That predestination includes the elect but not the reprobate. So on and so forth. From God's perfect simplicity to all of these other teachings (just to name a few), those who insist that "all we have is dogma (which they understand as being inclusive of solemn definitions and scripture)" don't actually act as if this were the case except when it comes to the issue of Baptism/BoD. They haven't the slightest clue that most of what is contained in the Deposit of Faith has never been solemnly defined.