Letters 65.12

Now, however, I am searching for the first, the general cause; this must be simple, inasmuch as matter, too, is simple. Do we ask what cause is? It is surely Creative Reason,—in other words, God. For those elements to which you referred are not a great series of independent causes; they all hinge on one alone, and that will be the creative cause.

Seneca, Letters to Lucilius 65.12, translated by Richard Mott Gummere