How did the author of Genesis know that God created the world?

Answer 1

The author of the Torah, in its entirety, was Moses (Deuteronomy 31:24), to whom God dictated its text (Exodus 24:12), including Genesis. Note also, that Genesis did not come to Moses as a surprise. The Israelites had always handed down the earliest traditions, even before Moses: What_did_the_early_israelites_read

According to tradition, there is only one Genesis creation-narrative, with ch.2 serving as an expansion of the brevity of ch.1, not a separate set of events (Rashi commentary, Gen.2:8). In ch.1, God created the universe from nothing (Exodus 20:11, Isaiah 40:28; Maimonides' "Guide," 2:30; Targum and Nachmanides on Gen. 1:1; Rashi commentary, Gen.1:14), and in ch.2, God performed specific acts within the broader picture.
The same literary devices which the Torah employs to enrich its text, have been used by Bible-critics in an attempt to reassign its authorship.

The Jewish sages, based on ancient tradition, identified many of these devices, which include:

recapping earlier brief passages to elucidate,

employing different names of God to signify His various attributes,

using apparent changes or redundancies to allude to additional unstated details,

speaking in the vernacular that was current during each era,

and many more. While Judaism has always seen the Torah as an intricate tapestry that nonetheless had one Divine source, some modern authors such as Wellhausen (the father of modern Biblical-criticism, 1844-1918) have suggested artificially chopping up the narrative and attributing it to various authors, despite the Torah's explicit statement as to its provenance (Exodus 24:12, Deuteronomy 31:24). This need not concern believers, since his claims have been debunked one by one, as Archaeology and other disciplines have demonstrated the integrity of the Torah. No fragments have ever been found that would support his Documentary Hypothesis, which remains nothing more than an arbitrary claim:

http://religion.answers.com/theory/debunking-the-jepd-documentary-hypothesis

http://www.apologeticspress.org/apcontent.aspx?category=6&article=1131(a Christian author)

Answer 2

The Book of Genesis had not one but at least three principal authors, now known as the Yahwist, the Elohist and the Priestly Source. The Yahwist wrote the second creation story (Genesis 2:4b-25) and the Priestly Source, several centuries later, wrote the first (Genesis 1:1-2:4a).
Each wrote what could have happened, not what the author really knew to have happened. It is because of different viewpoints of the two authors that their two creation stories differ so much in detail and even sequence. Because of faith, they each believed that God created the world, but did not know how this happened.

For more information, please visit: http://christianity.answers.com/theology/the-story-of-creation

Answer 3

According to The Bible, Moses was the author of Genesis and God revealed to him the events that transpired before his birth so that Moses could properly record those events.