Aquinas 2.
Primary and Secondary Principles.
Recap so far:
1. The Fundamental Precept – Do good, avoid evil
2. Use right reason to work out the real goods ie those that derive from our inclinations and so
contribute to our human flourishing.
3. From this, derive the precepts of Natural Law. Inclinations  Real Goods  Precept of NL
4. Following such precepts will be a good action, opposing them, a bad action.
Aquinas divides Natural Law into Primary and Secondary Principles.
Aquinas identifies 5 primary precepts, based on 3 essential aspects of our human nature that he
identifies, and that need to be followed, if we are to flourish as humans and achieve our end.
The 5 Primary Precepts are unchangeable, universal, exceptionless principles that hold at all times in
all places (cf. Cicero).
5 Primary Precepts (or Principles), based on 3 aspects of our human
nature:
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A. What man has in common with all substances –
1. Self-preservation: all things have an “appetite” for existing… even rocks!
- B. What man has in common with all creatures
2. drive to reproduce,
3. drive to educate and care for offspring (parental responsibility)
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C. What man has uniquely: his rational nature, made in the image of God
4. to know the truth (particularly the first Cause – God, and be united with Him)
5. to live in society.
The first two ends (A and B) will be relevant for man as a species to survive, but the third end (C), is
the ultimate end for every man - to rationally find his own self-fulfillment, culminating in union with
God. (God as First Cause, is man's full happiness).
To fulfill these 5 precepts is to function well as a human (cf. Aristotle).
We may not do anything that contradicts these fundamental drives in our nature, as then we are
going against God’s wise and right ordering of the world and of ourselves.
Prioritising And Integrating
We may prioritise and integrate these principles according to our own individual natures and reason :
we are not “forced” to positively obey physical nature, as if it was a tyrant over us. However, we may
not do anything that actually contradicts these drives.
Eg a man may become a celibate monk, as he is not actively contradicting any other drives –
although he is not fulfilling the drive to reproduction. He has rationally chosen to subordinate his
reproductive inclination to more directly achieve his higher end - union to God.
The following actions however, do contradict the 5 Precepts:
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Killing – because others, like yourself, have the inclination to self-preservation.
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Purposely insulting or offending those you live with, as this contradicts the natural law that
humans must live harmoniously in society with each other.
Stealing – this goes against principle to live peacefully in society with others.
Vomiting after eating to try and lose weight, as this directly contradicts the natural act of
eating for sustenance of the body’s functions. However, dieting by cutting out fats and sugars
is permissible as it does not detract from the proper functioning of the body.
Use artificial contraception during the act of sexual intercourse, or satisfy sexual desire in a
way that does not fit in with reproductive aims (eg homosexual sex, masturbation, oral sex
etc) since this is engaging in the act of reproduction in such a way that it directly contradicts
the nature of the reproductive act.
Human Laws & Secondary Precepts
A human law would be unjust if, it required, or even permitted murder, as this contradicts Natural Law - so
legally enforced abortions in China for women with unauthorized 2nd pregnancies
However, a human law may be just and correct, even if it contradicts NL. Such laws may even change
over time, or be different in different societies, without being wrong. For example:
 the state may legislate for capital punishment.
 Adultery is not a legal offence, even though it goes against 3rd precept of parental
responsibility.
 The state may legalise conscription, requiring people to sacrifice their lives in war.
 Universities or schools may charge fees that tend to exclude the poor.
PROBLEM: How is such a contradiction with natural law possible, which is meant to be universal
and eternal? The Primary Precepts are meant to be totally inflexible and unchanging!
(absolutist, deontological)
SOLUTION: Aquinas makes the comment:
"The general principles of the natural law cannot be applied to all men in the same way on account of
the great variety of human affairs, and hence arises the diversity of positive laws amongst various
people." (Summa Theologica I-II q.95)
In other words, we must take into account particular situations
before saying something is right or wrong. Aquinas does not think we
can determine the morality of actions by applying general principles
in a top-down way. We must always look at the features of a moral
situation, and from there, induce what the right action would be,
such that it does not tend to contradict NL, and works for the good
of society (the Common Good).
Aquinas comes up with the idea of Secondary Principles.
Secondary principles are derived from primary
principles, and should help support the primary principles. They are
only derived from the primary ones, and are based on a particular
human situation. Each situation is unique. Occasionally, it may
happen that secondary principles contradict the primary ones eg
conscription in time of war, celibacy, capital punishment.
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Examples of secondary precepts that CONTRADICT some primary precepts:
eg do not steal – but it may not be right to return property to its owner, if that owner will use it
against you.
“Now (to act according to reason) is true for the majority of cases: but it may happen in a particular
case that it would be injurious, and therefore unreasonable, to restore goods held in trust; for
instance, if they are claimed for the purpose of fighting against one's country” (ST I-II Q.94 art.4).
Eg do not steal – but if someone is in extreme need, it is their right to take it:
"It is not theft, properly speaking, to take secretly and use another's property in a case of extreme need:
because that which he takes for the support of his life becomes his own property by reason of that need." (ST I-II
Q.66)
eg do not kill, but it may be right to kill to stop a terrorist in his tracks.
Exterior and interior acts
When deciding what is right or wrong within a particular situation, 3 things are important – the
what/how, the why and the when:
1. the act itself (exterior act)– must not be in the class of “bad” acts
2. the intention/ motivation behind it (interior act) – for a real good
3. the particular situation involved
Aquinas calls the intention the “interior act” of the will
The act itself, ie.what you actually do, is the “exterior act”.
To perform a good act with a bad intention is also wrong
 Eg give to charity for a good reputation
 Eg help an old lady to gain her trust, so you can ask money from her later
 Eg to use contraception. This intention deprives the act of natural intercourse of the
procreative meaning, causing the sexual act to be non- natural.
To perform a bad act for a good intention, is wrong.
 Eg steal money to give to the poor
 Eg to spy to get intelligence for your country
 Eg doping in sports to win a race
 Eg to gamble wages for a family holiday
 Eg to use contraception to avoid AIDS
Clearly, because of the wrongness of the act itself, none of these can be justified . The following
quotes make the same point:
- The means never justifies the ends. It is always wrong to do evil that good may result. (Catechism
1759
- The Pauline Principle: you may not do evil, so that good can come of it (Rom.3:8)
- - "An evil action cannot be justified by reference to a good intention" (Aquinas, Dec. praec. 6).
- "Circumstances or intentions can never transform an act, intrinsically evil by virtue of its object,
into an act 'subjectively' good or defensible as a choice." (St.John Paul II: Veritatis Splendor, n. 81).
CASUISTRY & Probabilism
It is much more difficult to decide on Secondary Principles, as there may be many
factors in a sitaution that you need to consider. It is hard to be certain about such
moral judgements. Doing this, is called Casuistry.
Making Secondary Principles, through casuistry is error-prone because we are born
with Original Sin and make mistakes about what is truly good, but this is OK as it is
just part of being human. (St.Paul “all have sinned and fallen short of the glory of God” (Romans 3.23).
Here, conscience is a very important guide.
Secondary Principles make Aquinas’ NL theory flexible, but they can be abused to “make excuses” and
fudge the demands of the Primary Principles. This has given casuistry a bad name.
“This principle will be found to fail the more.. because the greater the number of conditions added, the greater
the number of ways in which the principle may failn”. (ST I-II q94 art.4)
Probabilism
(probable in this sense means “safe”
Probabilism is another form of casuistry. It says that in a difficult matter of conscience, where the law
is doubtful and unclear, there may be a reason why you could either follow it or not.
Eg can a Christian have a legitimate marriage with a non-believer? The New Testament is not
clear about this. The action is not certainly forbidden by law, so you may or may not do it, as
it is not fully forbidden. So how to decide?
Probabilism says: follow the general trend and follow the law (more probable)
However, if you are really struggling, and can find some backing from an
authoritative source, then this counts as having solid probability  you may
do it.
Eg. St Augustine said that a marriage between a Christian and a non-believer is
legitimate, since it is not clearly condemned in the New Testament. Augustine
is an authorithy in the Church, so this is good enough to stand as a solidly
probable opinion, and you now have a right to have such a marriage.
It is lawful to act on the less safe opinion if it is solidly probable, even if the safe
view is certainly more probable. Such casuistry, gives more freedom to people. But
others think that this kind of “making excuses” is bad practice, and permits actions
that ought to be forbidden, for their own good. However, the Church sees itself as
being the interpreter of its own laws, and that God is not more demanding or strict
than his own Church.
Equiprobabilism
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holds that it is not lawful to follow the less safe opinion when the safe opinion is certainly more
probable; or even when it is only equally probable with the safe opinion.
This view is associated with St. Alphonsus who was a lawyer, and as a lawyer he attached much
importance to the weight of evidence. A large body of evidence is what swings the case in a civil
action – so in a probabilistic scenario, the only solidly probably opinion is the one with more
evidence behind it.
Summary of Aquinas’ Natural Law Moral Theory
1. Recognise that Natural Law is derived from Eternal Law, so it is according to God’s wisdom that these
precepts should be followed. Humans have a duty to recognise these laws by their own reason, and act
accordingly, to find their final end in God. (deontological)
2. Use right reason, to discover your natural inclinations, and your real goods – precepts of NL (5 Primary
Principles) Do not act against these principles.
3. Derive secondary principles - considering the act, the intention and the situation itself.: they must be
good for the 2ndary Principle to be good (deontology). Don’t just apply Primary principles without
considering this, as every situation is different. Secondary principles should not go against primary ones,
only in exceptions, or specific historical contexts/ situations eg time of war.
4. Develop your virtues, so you can distinguish real from apparent goods. Live rightly so God will give you
the theological virtues (faith, hope, love) to direct you to your final end in Him.
5. Avoid Casuistry in the negative sense if possible. Options of Probabilism or Equiprobabilism if unclear
References
Summa Teologica – Aquinas/ Lisska - Aquinas / Kainz - Natural Law,/ International Theological
Commission - Natural Law/ Buckle, S. “Natural Law”,/ New Advent “Probabilism”/ Stanford
Encycl.Philosophy “Natural Law”, “Aquinas”