"By faith Noah, being warned of God of things not seen as yet, moved with fear, prepared an ark to the saving of his house; by the which he condemned the world, and became heir of the righteousness which is by faith." (Hebrews 11:7)
The little phrase "things not 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 evidence of things not seen. . . . Through faith we understand that the worlds were framed by the word of God, so that things which are seen were not made of things which do appear" (Hebrews 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 seen as yet" 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 that then was, being overflowed with water, perished" (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 Corinthians 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. HMM