When beginning to speak in detail of this ineffable Mystery of our Redemption, we must presuppose that it was the remedy and medicine for the universal fall and misery of mankind, and especially of the original sin through which mankind remained perverted and crippled. Since we cannot estimate the efficacy of a medicine unless we realise how serious is the malady, we must consider this first. For this we must understand first principles.
In order to understand this doctrine, we must take as its foundation the immense goodness of our Lord God, which is the principle of all His works and more particularly of this, which for its excellence is called the Work of God. As it is the nature of goodness to communicate its properties, it may be inferred that that supreme Goodness, which is the Divinity, is supremely communicative. Therefore, not content with having bestowed on His creatures their being and all they need to preserve it, His magnificence so surpassed this that, not satisfied with bestowing on them created gifts, He sought to add to them uncreated blessings, that is, communication and participation in his own bliss and glory. With this intention God created two kinds of beings, noble and capable of such great honour, namely, the angels, purely spiritual, and men who are both spiritual and corporeal. The latter, though on a much lower grade than the angels, equal them in the dignity of their final end.
We will say no more of the angels as they do not concern our subject but speak of men who were created by God for this destiny.