Sir Martin Rees on creatio ex nihilo and the Thomistic distinction between essence (essentia) and existence (esse)

     "Cosmologists sometimes claim that the universe can arise 'from nothing'.  But they should watch their language, especially when addressing philosophers.  We've realized ever since Einstein that empty space can have a structure such that it can be warped and distorted.  Even if shrunk to a 'point', it is latent with particles and forces — still a far richer construct than the philosopher's 'nothing'.  Theorists may, some day, be able to write down fundamental equations governing physical reality.  But physics can never explain what 'breathes fire' into the equations, and actualizes them in a real cosmos.  The fundamental question of 'Why is there something rather than nothing?' remains the province of philosophers.  And even they may be wiser to respond, with Ludwig Wittgenstein, that 'whereof one cannot speak, one must be silent'."

     Martin Rees, Just six numbers:  the deep forces that shape the universe (New York:  Basic Books, 2000 [1999]), 131.  I was put onto this by Aidan Nichols, Chalice of God:  a systematic theology in outline (Collegeville, MN:  Liturgical Press, 2012), 20-21, and have not actually read the book by Rees.