Since the 13th century Lateran IV teaching on creation was assimilated into the Vatican I Council, it is sufficient to examine the wording of the 1215 dogma to understand the significance of the term simul for the Vatican I fathers:
Deus…creator omnium visibilium et invisibilium, spiritualium et corporalium: qui sua omnipotenti virtute simul ab initio temporis utramque de nihilo condidit creaturam, spiritualem et corporalem, angelicam videlicet et mundanam: ac deinde humanam, quasi communem ex spiritu et corpore constitutam.
In the following Denzinger English translation, the underlined word simul in Latin is translated as “at once” connoting direct creation (from nothing):
God…creator of all visible and invisible things, of the spiritual and of the corporal; who by His own omnipotent power at once from the beginning of time created each creature from nothing, spiritual and corporal, namely, angelic and mundane, and finally the human, constituted as it were, alike of the spirit and the body (D.428).
A reference in the French text of the CCC (327) should be taken as definitive since it translates simul as “tout ensemble,” i.e. all things were created together. It reads:
La profession de foi du quatrième Concile du Latran affirme que Dieu « a tout ensemble », dès le commencement du temps, créé de rien l’une et l’autre créature, la spirituelle et la corporelle, c’est-à-dire les anges et le monde terrestre ; puis la créature humaine qui tient des deux, composée qu’elle est d’esprit et de corps.
Yet despite the identical meaning of these translations a second diametrically opposed meaning was introduced in the latter part of the nineteenth century allowing for things to be created at intervals over millions of years. As the Council’s dogma says that “all things” were created “at once from the beginning of time,” the conflict between the two meanings is more than transparent.