We know of the wonders that God has done from time to time, so we know that His power is great and wonderful, the Bible itself shows us and speaks of His power and majesty that dwell in Him.
In Romans we find the Apostle Paul speaking of the greatness of God, this man speaks of the power of God, praising the greatness. Let us remember well who this man was according to the Scriptures.
Paul speaks of the power of God because He appeared in his life and was greatly blessed because he knew of God and since then his life changed, even his name was changed.
19 Because that which may be known of God is manifest in them; for God hath shewed it unto them.
20 For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
The power of God becomes visible every day, because His work does not stop, but at every moment we see God make His power visible, for this reason we have not seen Him, but we believe and have this certainty of His great power and glory.
Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
This happened with these men who did not recognize the power of God, did not glorify Him, and did not thank Him, but their heart went straight to do evil and their heart was darkened in the entirety.