As we know, this magnificent angel – the greatest creature God had created up to that time – disobeyed God and fell into apostasy, and in so doing brought one third of the other angels with him. The angels who thought to themselves, “we would rather be wrong with Lucifer than right without him”, got their wish and became demons, while those who remained faithful to God, in spite of the apostasy of their divinely appointed leader, were immediately confirmed in grace and now reign with God in heaven.
After the fall of the bad angels, God created man. He endowed the first man with the preternatural gifts of integrity, bodily immortality, impassibility, and infused knowledge, which perfected him according to nature, as well as the supernatural gift of grace, which elevated his soul to the supernatural level, thereby making him a “partaker of the Divine Nature” (2 Peter 1:4). By the gift of infused knowledge, Adam knew all that he had a natural aptitude to know (2), including knowledge of the physical universe, both material and spiritual, the moral law, the Divine Attributes of God, and man’s relationship to his creator” (3), as well as the supernatural knowledge necessary to guide him and his descendants to their supernatural end. (4) All of the gifts Adam received would have been passed down to his posterity, with the exception of infused knowledge.
The reason his descendants would not have received this gift, according to St. Thomas, is because Adam was to be the teacher of all other men. (5) As father of the human race, he was to instruct and govern mankind, just as Lucifer was to govern and enlighten the lower angels. As we know, Adam, the father of the human race and divinely appointed teacher of all men, disobeyed God and fell into sin, thereby causing the Fall of the entire human race. But unlike the angels who fell, God did not abandon man, but instead promised to send a Redeemer.