1. Natural Law Ethics Always act so as to pursue good and to avoid evil.
Basic goods are prescribed to us by God through natural law.
The Intention of an act in pursuing Good and shunning evil determines its morality

2. ‘The law is right reason in agreement with nature’
Sources
‘The natural is that which is equally valid and depends not on being or not being ... It is unchangeable’
Aristotle Nicomachean Ethics: Book V Chapter 7
‘The law is right reason in agreement with nature’
Cicero De Republica III xxii

3. Paul & Romans 2:14-15
“The Gentiles do not have the Law; but they do by instinct what the Law commands, they are their own law, even though they do not have the Law. Their conduct shows that what the commands say, is written in their hearts. Their consciences also show that this is true, since their thoughts sometimes accuse them and sometimes defend them.”

4. Natural Purposiveness in Nature
Aristotle on Essential Form
As a thing changes its Essential form remains the same and makes it what it is and guides it to its goal or telos.

5. Purposiveness in Nature
All natural change is an actualization of potential:
Change is a movement of a natural form towards a telos or end or goal.
The Goal is prescribed by God though his creation of natural objects and their laws.

6. Figure 1. The hierarchical structure of law.
The nature of Law
  Figure 1. The hierarchical structure of law.
                                                                                      Eternal law                 the realm of the supernatural           ↕                                                                                      Divine law                                                    ↕                                                                                           Natural law                                         the realm of the natural                                ↕                                                                                 Human law

7. First Principle of Morality St. Thomas Aquinas(1225-1274)
Do Good and Avoid Evil
You must always act with the intention of honoring good and never with the intent of producing evil.

8. Continuation of the species through reproduction
Primary Precepts
Aquinas:
Self – preservation
Continuation of the species through reproduction
Educate children
Live in society
Worship God

9. Contemporary Versions
life
truth and knowledge of it
physical and mental health
procreation
practical reasonableness
aesthetic value
social life
authenticity
excellence in work and play
justice
friendship and community
integrity 
self-integration and inner peace
pleasure and the avoidance of pain

10. Secondary Precepts
Do not kill.
Do not lie.

11. Casuistry The application of natural law to particular cases.
Requires practical rationality.

12. There will be cases where two different goods might conflict.
Double Effect
There will be cases where two different goods might conflict.
In these cases there are two different effects for the act. One may act to pursue the good and to avoid evil be directing one’s intentions to one of the goods without intending to harm the other.

13. Example: Self Defense Killing an assailant has two effects:
Taking the life of the attacker.
Saving your life
You may act to preserve your life as long as you do not actively intend to harm the good of life in the person of the attacker.

14. Intentions Direct intention and Secondary Intention
The good must be your primary intention, not your secondary intention.
Primary intention defines the act. If you plant a seed, your primary intention is to put the seed in the soil.
Secondary intention are the other intended effects of the action, such as to feed your family.

15. Conditions for Application of Double Effect.
The doctrine consists of four conditions that must be satisfied before an act is morally permissible:
1. The nature-of-the-act condition. The action must be either morally good or indifferent.
2. The means-end condition. The bad effect must not be the means by which one achieves the good effect.
3. The right-intention condition. The intention must be the achieving of only the good effect, with the bad effect being only an unintended side effect.
4. The proportionality condition. The good effect must be at least equivalent in importance to the bad effect.