St. Thomas Aquinas
Natural law theory
Just war theory

Natural Law is a set of morals, based on what are

assumed to be the everlasting characteristics of human

nature, that serves as a standard for evaluating conduct

and civil laws. It is considered essentially enduring and

astronomically relevant, because of the double meaning of

the word nature, the meaning of natural varies. Thus,

natural law may be considered an ideal to which humanity

aspires or a general fact, the way human beings usually

act. Natural law is contrasted with positive law, the

enactment’s of civil society.

Christians found the natural law ideology of the Stoics

quite compatible with their beliefs. The teaching of St.

Thomas Aquinas on the natural law is the most widely known.

Aquinas called the rational guidance of creation by God the

“Eternal Law." The Eternal Law gives all beings the

tendency of these actions and aims that are proper to them.

Rational creatures, by directing their own actions and

guiding the actions of others, share in godly reason

itself. “This participation in the Eternal Law by rational

creatures is called the Natural Law." Its dictates

correspond to the basic bias of human nature. Thus,

according to Aquinas it is possible to distinguish good

from evil by the natural light of reason.

Just War, based on Roman thought, is the traditional

Roman Catholic position on fighting a war. It lays down the

criteria for fighting a war. Just cause, declares, waged by

legitimate political authority. War must be started as last

resort. Just methods must be used in war. Must expect

flourishing outcome of war. Results must be less evil that

if war not undertaken. Worriers must have just intentions.

Finally, war must be carried out as a path to better

condition of peace.