“By faith Noah, being warned by God about things not yet seen, in reverence prepared an ark for the salvation of his household, by which he condemned the world, and became an heir of the righteousness which is according to faith.” Hebrews 11:7
The little phrase “things not yet seen” is used three times in the New Testament, and interestingly enough, these refer to the past, present, and future works of God with respect to the things that are seen.
At the beginning of the “faith chapter” of Hebrews occur these remarkable words “Now faith is the assurance of things...not seen...By faith we understand that the worlds were prepared by the word of God, so that what is seen was not made out of things which are visible” (Heb. 11:1, 3). That is, the material things of this present world were not made of pre-existing materials - they were supernaturally created by the word of the Creator! These things which are now seen provide evidence (or better, the “conviction”) of the things not seen – that is, of God’s creative work completed in the past.
The “processes” that are now seen (as distinct from the “materials”) date especially from the time of the great Flood. The “things not yet seen” by Noah - that is, the present atmospheric circulation, the present hydrological cycle, the present seasonal changes, and many other key phenomena of the present order, all were instituted in the days of Noah when “the world at that time was destroyed, being flooded with water” (2 Peter 3:6).
Finally, “we look not at the things which are seen, but at the things which are not seen; for... the things which are not seen are eternal” (2 Cor. 4:18). Just as surely as the materials and processes of the present world once were unseen, but now are easily seen, so the future eternal world will soon be clearly seen when Christ returns.