What does 'by Him all things consist' mean?
The phrase 'by Him all things consist' means that God the Son holds the entire universe together. He controls every particle by the power of His Word, preventing nuclear fission from exploding the cosmos and keeping planets from splitting apart. All things are held together by Him.
Les explains that in Colossians 1:17, after stating that all things were created by the Son—visible and invisible, thrones, dominions, principalities, even Satan—and created for Him and His purposes, Paul declares that He is before all things and by Him all things consist. Les says the word 'consist' means 'held together.' He illustrates this by asking why the universe does not explode in nuclear fission or why planets do not act like an atom and split one another into tremendous energy and explosion. He thinks someday they will, but not tonight, because God the Son controls every particle of it with His Word, with the power of His Word.
And he is before all things, and by him all things consist.