As I've said before, theology and doctrine are two different things. It is a doctrine that women can't be priests; whereas around a year ago I gave a theological reason why women can't be priests. This is not the only reason, or theology, but it's the one I like the best.
It is possible for two different theologies to disagree with each other. This is the case with the predestination of the Incarnate. Thomistic theology, which almost engulfs the entirely Roman Church, says that the predestination of the Incarnate was conditioned. On the other hand, Franciscan theology, specifically Scotistic theology, says that it was unconditioned.
Let me simplify this:
The Incarnation is the doctrine that the Second Person of the Trinity (the Son) became man. "And the Word was made flesh and dwelt among us." (John 1:14)
Conditional predestination of the Incarnation is the belief that Christ became man because of the sin of Adam. Sin was necessary so that Christ could come and redeem mankind. Theoretically, if there was no Fall, there would be no Incarnation. This is where the felix culpa in the Exsúltet comes from: "O happy fault, O necessary sin of Adam, that gained for us so great a Redeemer!" The fact that we will all hear this chanted next week during the Easter Vigil only proves how dominating Thomistic theology is in the Roman Church.
Unconditioned predestination of the Incarnation is the belief that Christ became man to crown His creation. Theoretically, Christ would have become man with or without the Fall. The Incarnation was the goal of creation, not a solution to sin.
Last year, I gave a couple examples of John Paul the Great's Theology of the Body that supported the unconditioned predestination of the Incarnation. Over the last year, I've found a couple more passages in other literature.
The first one is found in no. 22 of the Vatican II document Gaudium et Spes:
The truth is that only in the mystery of the incarnate Word does the mystery of man take on light. For Adam, the first man, was a figure of Him Who was to come, namely Christ the Lord. Christ, the final Adam, by the revelation of the mystery of the Father and His love, fully reveals man to man himself and makes his supreme calling clear.
The second is a quote of St. Lawrence of Brindisi, Doctor of the Church:
God is love, and all his operations proceed from love. Once he wills to manifest that goodness by sharing his love outside himself, then the Incarnation becomes the supreme manifestation of his goodness and love and glory. So, Christ was intended before all other creatures and for his own sake. For him all things were created and to him all things must be subject, and God loves all creatures in and because of Christ. Christ is the first-born of every creature, and the whole of humanity as well as the created world finds its foundation and meaning in him. Moreover, this would have been the case even if Adam had not sinned.
It wouldn't be fair if I didn't give a quote from the opposing side. St. Augustine, a forerunner of St. Thomas Aquatis and also a Doctor of the Church, has this to say:
If mankind had not fallen, the Son of man would not have come... Why did He come into the world? To save sinners (1 Timothy 1:15). There was no other reason for His coming into the world
I believe that the Thomistic view on this topic is wrong. I would even go so far as to say that it is an error, but that would be over stepping my boundaries, which I did last year.
What is demonstrated, though, is that there can be two conflicting theologies over that same doctrine. The Incarnation is a doctrine. Whether the predestination of the Incarnation was conditional or unconditional is entirely theological.