We believe that God created the world according to his wisdom. It is not the product of any necessity whatever, nor of blind fate or chance. We believe that it proceeds from God’s free will; he wanted to make his creatures share in his being, wisdom and goodness: “For you created all things, and by your will they existed and were created.” Therefore the Psalmist exclaims: “O LORD, how manifold are your works! In wisdom you have made them all”; and “The LORD is good to all, and his compassion is over all that he has made.” God creates “out of nothing” 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. God creates freely “out of nothing”: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.Scripture bears witness to faith in creation “out of nothing” as a truth full of promise and hope. Thus the mother of seven sons encourages them for martyrdom:I do not know how you came into being in my womb. It was not I who gave you life and breath, nor I who set in order the elements within each of you. Therefore the Creator of the world, who shaped the beginning of man and devised the origin of all things, will in his mercy give life and breath back to you again, since you now forget yourselves for the sake of his laws. . . Look at the heaven and the earth and see everything that is in them, and recognize that God did not make them out of things that existed. Thus also mankind comes into being.
Since God could create everything out of nothing, he can also, through the Holy Spirit, give spiritual life to sinners by creating a pure heart in them, and bodily life to the dead through the Resurrection. God “gives life to the dead and calls into existence the things that do not exist.” and since God was able to make light shine in darkness by his Word, he can also give the light of faith to those who do not yet know him.
From the Catechism of the Catholic Church 295-298