1. “It cannot be denied, in spite of frequent interpretations of Genesis 1 that departed from the rigidly literal, that the almost universal view of the Christian world until the eighteenth century was that the Earth was only a few thousand years old.” Davis A. Young, Christianity and the Age of the Earth (Grand Rapids: Zondervan Publishing House, 1982), p. 25.
u “... given that virtually everyone in the Western world until well into the eighteenth century still believed in a cosmos that was only a few thousand years old, almost no one was prepared to suggest that the work described in the first two verses of Genesis 1 lasted tens of thousands of years or even more prior to the work of the six days.” Davis A. Young and Ralph F. Stearley, The Bible, Rocks and Time (Downers Grove, Illinois: InterVarsity Press, 2008), p. 120.
2. The best defense of the gap theory is Without Form and Void by Arthur C. Custance. His stated motivation for supporting the gap theory, as his widow explained to me in a letter in about 1996, was to satisfy those demanding an old Earth. Custance had written:
Furthermore, if a vast antiquity far beyond the 4000 BC traditional date is demanded [for the date of creation], there are other ways in which a great antiquity for the world prior to the creation of man can be allowed for. For example, the days of Genesis might be viewed as days on which revelation was given to Moses; or they might be taken to mean ages; or we may introduce a hiatus between Genesis 1:1 and 1:2, and so on. Arthur C. Custance, Two Men Called Adam (Brockville, Ontario: Doorway Publications, 1983), p. 246.
While Custance wavered on the question of the Earth’s age, he favored a young Earth.
And I do not think that the biblical account can ever be made to accommodate the antiquity that is still being demanded. Personally, I am convinced that the arguments for this vast antiquity will in due course be modified by fresh evidence and the Bible vindicated, as it always has been. Ibid., p. 249.
3. Some believe that names are omitted in the genealogies of Genesis. This would not alter the stated lengths of time between generations. [See "According to the Bible, When Was Adam Created?" on page 513.]
4. For the most thorough discussion and critique of the gap theory, see Weston W. Fields, Unformed and Unfilled: The Gap Theory (Grand Rapids: Baker Book House, 1976).