Legal syllogisms generally have three sources of major premises.
Legislation (constitution, statute, regulation, ordinance,
Policy (i.e., consequences of the decision)
The minor premise comes from the facts. Legal reasoning usually
revolves around these minor premises/facts. When the court
applies agreed upon legal principles to undisputed facts the case
3 Major premise—Facts A produce Legal Outcome B.
3 Minor premise—The Facts here are like A.
3 Conclusion— Therefore, Legal Outcome B.
But without an agreed-upon legal principle, the major premise
must come from induction. The court either must analogize to a
precedent or induce from many cases.
Attacking Legal Logic
Two thousand years ago, Cicero articulated the formula for argu-
Every argument is refuted in one the these ways: either one
or more of its assumptions are not granted; or if the assump-
tions are granted, it is denied that a conclusion follows from
them; or the form of augment is shown to be fallacious; or a
strong argument is met by an equally strong or stronger.
Breaking Cicero down in three parts, we can see how to refute
First, Cicero recommends attacking your opponent’s syllogism:
“either one or more of its assumptions are not granted; or if
the assumptions are granted, it is denied that a conclusion
follows from them”
The following applies this to the modern legal syllogism:
The law = major premise
The facts = minor premise
Ergo = The conclusion follows
The lawyer’s argument would be something like,
The other side is using the wrong law.
The other side got the facts wrong.
The facts do not fit the law here.
Second, Cicero notes we can attack our opponents’ Logical
“the form of augment is shown to be fallacious”
A fallacy is an argument that looks like a conclusive syllogism, but
does not establish the conclusion.
5 As Aristotle recognized,
“that some [lines of] reasoning are genuine, while others
seem to be so but are not, is evident. This happens with
arguments, as also elsewhere, through a certain likeness
between the genuine and the sham.”
Often, when a party claims in a motion or brief that the opponents “reasoning is flawed … ,” they are not really pointing out a
logical error, just a disagreement with their opponent’s major
premise. As the following demonstrates, however, we can define
fallacies in logic.
25 JANUARY 2014 ARIZONA ATTORNEY www.azbar.org/AZAttorney
7. Aristotle and slavery: Even a truly great thinker can fall into logical fallacy. Aristotle did not base slavery on
race, contrary to arguments in the American south before the Civil War. Rather for Aristotle, nature establishes
hierarchies: Men are superior to animals and women; masters are superior to slaves. The “natural” difference
between masters and slaves had to do with different abilities to reason. Some men possess reason while others
can only perceive reason. If you possess reason you are by nature a master and if you lack it you are by nature
a slave. The universality of slavery underscored for Aristotle its basic nature. Of course, if Aristotle followed his
own rule to study “what actually happens” he would have seen that any number of “masters” lack capacity to
reason and any number of slaves are far more intelligent and reasonable than their “masters.” Aristotle’s view on
slavery is literally “the classic” example of the naturalist fallacy, where the observer takes as “natural” his own
limited historical and social perspective. Because Aristotle could not imagine a world without slavery, it had to
be “natural.” See generally ARISTOTLE, POLITICS
55–63 (Benjamin Jowett trans., Random House 1943).
In fact, Aristotle’s own philosophical tools show the fallacy of his thinking on slavery. Applying the syllogism
to Aristotle’s view on slavery gives the following:
If men are “naturally” different, and if masters have “reason” and slaves do not, then slavery is “natural.”
But the value of the syllogism depends not only on the truth of both the first and second premise, but also
on the equation’s order. Surely men are different, but the second premise that masters have reason and slaves
do not, does not stand up to observation. Although it may have been subjectively true for Aristotle, it is objectively
Instead of a syllogism, it becomes a tautology, a statement that was true merely by virtue of saying the
same thing twice.
If A and B; or not A; or not B
Aristotle’s view of slavery is no more sophisticated than the following tautology:
Slavery shows that men are naturally different; or a master is naturally not a slave; or a slave is naturally not a master.
A tautology has limited rhetorical value and no logical value. The fact that Aristotle had sophisticated tools to see the fallacy of his own views on slavery cuts
against excusing him as “just a man of his time.” Rather, it diminishes him.
Marcus Tullius Cicero
Attack the analogy
Attack the facts
Attack the facts
Attack the analogy
The conclusion is non sequitur