Consider the difficulty... in the statement that time existed before the creation of the sun! We shall undoubtedly soon remove this difficulty... All things were created together, but were separated from each other successively...Abarbanel, Commentary to Genesis, p. 10:
The account of the six days of creation contains, in reference to the creation of man, the statement: “Male and female He created them” (1:27), and concludes with the words: “Thus the heavens and the earth were finished, and all the host of them” (2:1), and yet the portion which follows describes the creation of Eve from Adam, the tree of life, and the tree of knowledge, the history of the serpent and the events connected therewith, and all this as having taken place after Adam had been placed in the Garden of Eden. All our Sages agree that this took place on the sixth day, and that nothing new was created after the close of the six days. None of the things mentioned above is therefore impossible, because the laws of Nature were then not yet permanently fixed. There are, however, some utterances of our Sages on this subject [which imply a different view]. I will gather them from their different sources and place them before you, and I will refer also to certain things by mere hints, just as has been done by the Sages. You must know that their words, which I am about to quote, are most perfect, most accurate, and clear to those for whom they were said. I will therefore not add long explanations, lest I make their statements plain, and I might thus become “a revealer of secrets,” but I will give them in a certain order, accompanied with a few remarks, which will suffice for readers like you.
The Rambam believed that there were not separate creative acts on six days, but rather everything was created on one day, in a single instant. In the work of Creation, there is mention of “six days” to indicate the different levels of created beings according to their natural hierarchy; not that there were actual days, and nor that there was a chronological sequence to that which was created in the acts of Genesis… This is the view of the Rambam which he considered as one of the major secrets of the Creation. He tried to conceal this view with ingenuity, as can be seen in his words there. But Ralbag went and tattled, revealing his secret, as did Narboni and the other commentators to his work; they uncovered his secret and publicized his view….
The Rav, the Guide, gave the reason for the mention of Days in the Beginning by explaining the statement of the Sages, who said that “all the products of Creation were created in their full form” (Talmud, Chullin 60a); in other words, everything was created at the first instant of creation in their final perfect form. Thus the mention of an order of Creation is not describing the sequence of days; rather, [but the days are simply serving] to differentiate the status of [the elements of creation] and to make known the hierarchy of nature. This was [Rambam’s] major esoteric doctrine concerning Creation as those who are understanding can discern from that chapter (Guide For The Perplexed 2:30) which is devoted to this extraordinary account.
Maimonides' view of the original sin is thus allegorical. As he states in Guide 2:30 regarding the dicta of the Sages about Adam and Eve in the Garden of Eden: "Their allegorical interpretation was clear to those to whom it was addressed, and they [the dicta] are unambiguous." Referring to some of these dicta, which he describes as "amazing," Maimonides further states that "their external meaning is exceptionally incongruous, but ...when you obtain... true understanding, you will admire the wisdom of these parables." (p.187)Rabbi Moshe Meiselman, in Torah, Chazal and Science:
...The Rambam limits the use of allegory to the Nevi'im. Consequently it may not be invoked with respect to the Creation narrative, which is part of the Chumash... The Rambam took the opening chapters of Bereishis completely literally, albeit neither simplistically nor superficially... Mori veRebbi, ztz"l, never suggested at any stage in his thinking that anything in Sefer Bereishis could be taken allegorically. On the contrary, he insisted that all the narrative be taken in their most literal sense. This was essential because what made the moral lessons in them true was the fact that the events actually occurred precisely as described." (pp. 391, 415, 650)