From this it is evident that we have already met the next statement of Celsus, which is as follows: “We must either not live, and indeed not come into this life at all, or we must do so on condition that we give thanks and first-fruits and prayers to demons, who have been set over the things of this world: and that we must do as long as we live, that they may prove good and kind.” We must surely live, and we must live according to the word of God, as far as we are enabled to do so.
And we are thus enabled to live, when, “whether we eat or drink, we do all to the glory of God;” and we are not to refuse to enjoy those things which have been created for our use, but must receive them with thanksgiving to the Creator. And it is under these conditions, and not such as have been imagined by Celsus, that we have been brought into life by God; and we are not placed under demons, but we are under the government of the Most High God, through Him who has brought us to God— Jesus Christ.
It is not according to the law of God that any demon has had a share in worldly affairs, but it was by their own lawlessness that they perhaps sought out for themselves places destitute of the knowledge of God and of the divine life, or places where there are many enemies of God. Perhaps also, as being fit to rule over and punish them, they have been set by the Word, who governs all things, to rule over those who subjected themselves to evil and not to God. For this reason, then, let Celsus, as one who knows not God, give thank-offerings to demons.
But we give thanks to the Creator of all, and, along with thanksgiving and prayer for the blessings we have received, we also eat the bread presented to us; and this bread becomes by prayer a sacred body, which sanctifies those who sincerely partake of it.
Source: Against Celsus (New Advent)