CCC 296 We believe that God needs no pre-existent thing or any help in order to create, nor is creation any sort of necessary emanation from the divine substance.1 God creates freely “out of nothing”:2
If God had drawn the world from pre-existent matter, what would be so extraordinary in that? A human artisan makes from a given material whatever he wants, while God shows his power by starting from nothing to make all he wants.3
1 Cf. Dei Filius, can. 2-4: DS 3022-3024.
2 Lateran Council IV (1215): DS 800; cf. DS 3025.
3 St. Theophilus of Antioch, Ad Autolycum II, 4: PG 6,1052.