Is the Gap Theory Credible?

Concerning biblical interpretations (exegesis) of Creation among Christians, there is a belief called "The Gap Theory." Actually, it is less than a theory because theories are based upon hypothetical circumstances which are merely assumed conditions. This gap theory is also known as "The Ruin and Restoration Theory." At the outset, the writer states that he does not believe in the "so called" Gap Theory. However, many fine Christian brethren do believe in some form of it. Advocates of this theory believe that there is a gap of indeterminate (uncertain) time between the verses of Genesis 1:1 and Genesis 1:2. The claim is that a former civilization (probably satanic and possible human-kind) existed between the two verses of Genesis 1:1 and Genesis 1:2. This "alleged" pre-Adamite civilization was supposed to be guilty of corrupting earth. The gap theorists claim a gap of time, longer than a 24-hour solar day (?), occurred when chaos reigned upon earth after the first day of God's Creation. However, it would be hard to reconcile a proposed former creation of earth, with animals, vegetation, and human life, because there was no habitable earth (neither life forms) existing between Genesis 1:1 and Genesis 1:2. You would have to assume that an entire, finished world was completed at the end of Genesis 1:1. There is no mention of a formed world. Land did not appear until the third day of Creation (Genesis 1:9). Life forms did not appear until the third, fifth and sixth day. Conclusion: Neither an angel, life form, or a mortal man could exist upon an earth that did not yet exist.