He next, in many words, blames us for asserting that God made all things for the sake of man. Because from the history of animals, and from the sagacity manifested by them, he would show that all things came into existence not more for the sake of man than of the irrational animals. And here he seems to me to speak in a similar manner to those who, through dislike of their enemies, accuse them of the same things for which their own friends are commended. For as, in the instance referred to, hatred blinds these persons from seeing that they are accusing their very dearest friends by the means through which they think they are slandering their enemies; so in the same way, Celsus also, becoming confused in his argument, does not see that he is bringing a charge against the philosophers of the Porch, who, not amiss, place man in the foremost rank, and rational nature in general before irrational animals, and who maintain that Providence created all things mainly on account of rational nature.
Rational beings, then, as being the principal ones, occupy the place, as it were, of children in the womb, while irrational and soulless beings hold that of the envelope which is created along with the child. I think, too, that as in cities the superintendents of the goods and market discharge their duties for the sake of no other than human beings, while dogs and other irrational animals have the benefit of the superabundance; so Providence provides in a special manner for rational creatures; while this also follows, that irrational creatures likewise enjoy the benefit of what is done for the sake of man.
And as he is in error who alleges that the superintendents of the markets make provision in no greater degree for men than for dogs, because dogs also get their share of the goods; so in a far greater degree are Celsus and they who think with him guilty of impiety towards the God who makes provision for rational beings, in asserting that His arrangements are made in no greater degree for the sustenance of human beings than for that of plants, and trees, and herbs, and thorns.
Source: Against Celsus (New Advent)