This treatise and that which follows it form in reality two parts of a single work. Jerome (De Script. Eccl.) refers to them as 'Adversus Gentes Libri Duo.' They are, however, more commonly distinguished by the titles given them in the present volume. Both books, indeed, are mainly directed against the Gentiles, but in the present treatise the refutation is carried out with more special reference to the beliefs and worship of the heathen. The two books belong to the earlier years of Athanasius. The Arian controversy which broke out (319 a.d.) probably before his twenty-second year has left no trace upon them (not even c. Gent. 46. 8, see note there). How long before the limit thus fixed the work was composed it is impossible to say with certainty. The hint (c. Gent. 9. 5) that the time for the deification of emperors by decree of the Senate might have come to an end points to the conversion of Constantine as a terminus a quo. And the full maturity of power which marks out the de Incarnatione as a masterpiece of Christian theology inclines us to put the composition as late as we can. Hence the date usually adopted, viz. in or shortly before 318 b.c., the twenty-first year (probably) of Athanasius' age.
The position of the book in relation to the general history of the theology of Athanasius and of the Church has been pointed out in the Prolegomena. It remains to sketch its argument, and tabulate its arrangement: a somewhat more extended summary is prefixed to each section.
His aim is to vindicate (S:1) the Dignity and reasonableness of the Christian Faith. The main vindication of the Faith is seen in its practical results. But, that these may produce their proper effect, a removal of error from the mind is needed. Hence the necessity of refuting idolatry, which is deduced from the same cause as evil in general, namely, the departure of man from his original exemplar, the Logos (S:S:2-5). By the misuse of his power of conscious choice, man fell (6-8) into the degradation and illusions (9-15) of idolatry. He then examines the popular and learned pleas on behalf of idolatry (16-26), and thus arrives at the central problem of the conception of God. That God is not Nature is shewn (27-29) by the mutual dependence of the various constituents of the Universe: no one of these, therefore, can be God: nor can their totality; for God is not compounded of parts on which He depends, but is Himself the cause of existence to all. Such a God as this, the soul of man (30-33) can and, if purified from sin, will (34) recognise; if her imperfections hinder this, the spectacle of Reason and Order in the Universe (35-46) will assist her to recognise the handiwork of God, and the presence of the Logos, and through him the Father. The reclamation and restoration of sinful and degraded man can only be effected (47) by a return to the Logos. This opens the question dealt with in the second book, de Incarnatione.
Reference address : https://www.elpenor.org/athanasius/contra-gentes-introduction.asp