St. Thomas Aquinas is a famous philosopher and theologist who was born in Roccasecca, Italy where he joined the Dominican order while studying philosophy and theology at Naples. He then seeked additional studies in Paris and Koln. There he was exposed to Aristotelean thought by Albert the Great and William of Moerbeke.
Aquinas taught in Paris and Rome for the remainder of his life while writing millions of words on philosophical and theological issues. "The Angelic Doctor" developed a massive synthesis of Christianity and Aristotelian philosophy that later became the Roman Catholic theology in 1879.
"The Angelic Doctor" believed that in some circumstances genuine knowledge was led to by human reason. He believed that by being human, we naturally rely on sensory information for our knowledge of the world.
Even in the lost the natural inclination to virtue remains, else they would have no remorse of conscience.
As regards the individual nature, woman is defective and misbegotten, for the active power of the male seed tends to the production of a perfect likeness in the masculine sex; while the production of a woman comes from defect in the active power.
Because of the diverse conditions of humans, it happens that some acts are virtuous to some people, as appropriate and suitable to them, while the same acts are immoral for others, as inappropriate to them.
By nature all men are equal in liberty, but not in other endowments.
Clearly the person who accepts the Church as an infallible guide will believe whatever the Church teaches.
Friendship is the source of the greatest pleasures, and without friends even the most agreeable pursuits become tedious.
Human law is law only by virtue of its accordance with right reason, and by this means it is clear that it flows from Eternal law. In so far as it deviates from right reason it is called an Unjust law; and in such a case, it is no law at all, but rather an assertion of violence.
Man has free choice, or otherwise counsels, exhortations, commands, prohibitions, rewards and punishments would be in vain.
Therefore it is necessary to arrive at a prime mover, put in motion by no other; and this everyone understands to be God.