Prior Analytics is Aristotle's work on deductive reasoning, specifically the syllogism. It is also part of his Organon, which is the instrument or manual of logical and scientific methods.
The Prior Analytics represents the first formal study of logic. In it, Aristotle identifies valid and invalid forms of arguments called syllogisms. A syllogism is an argument consisting of three sentences: two premises and a conclusion. Each proposition of a syllogism is a categorical sentence which has a subject and a predicate connected by a verb. There are four different types of categorical sentences: universal affirmative (A), particular affirmative (I), universal negative (E) and particular negative (O).
Prior Analytics is Aristotle's work on deductive reasoning, specifically the syllogism. It is also part of his Organon, which is the instrument or manual of logical and scientific methods.
Analytics comes from the Greek word "analutos" meaning "solvable" and the Greek verb "analuein" meaning "to solve". However, in Aristotle's corpus, there are distinguishable differences in the meaning of "analuein" and its cognates. There is also the possibility that Aristotle may have borrowed his use of the word "analysis" from his teacher Plato. On the other hand, the meaning that best fits the Analytics is one derived from the study of Geometry and this meaning is very close to what Aristotle calls έπιστήμη "episteme", knowing the reasoned facts. Therefore, Analysis is the process of finding the reasoned facts.^{[1]}
Of the entire Aristotelian corpus, Aristotle gives priority to the study of his treatises on Logic. However, he never gave a general name to his treatises on Logic nor did he coin the word Logic. Aristotle's Prior Analytics represents the first time in history when Logic is scientifically investigated for the first time. On those grounds alone, Aristotle could be considered the Father of Logic for as he himself says in Sophistical Refutations, "... When it comes to this subject, it is not the case that part had been worked out before in advance and part had not; instead, nothing existed at all." ^{[2]}
A problem in meaning arises in the study of Prior Analytics for the word "syllogism" as used by Aristotle in general does not carry the same narrow connotation as it does at present; Aristotle defines this term in a way that would apply to a wide range of valid arguments. Some scholars prefer to use the word "deduction" instead as the meaning given by Aristotle to the Greek word συλλογισμός "sullogismos". At present, "syllogism" is used exclusively as the method used to reach a conclusion which is really the narrow sense in which it is used in the Prior Analytics dealing as it does with a much narrower class of arguments closely resembling the "syllogisms" of traditional logic texts: two premises followed by a conclusion each of which is a categorial sentence containing all together three terms, two extremes which appear in the conclusion and one middle term which appears in both premises but not in the conclusion. In the Analytics then, Prior Analytics is the first theoretical part dealing with the science of deduction and the Posterior Analytics is the second demonstratively practical part. Prior Analytics gives an account of deductions in general narrowed down to three basic syllogisms while Posterior Analytics deals with demonstration.^{[3]}
In the Prior Analytics, Aristotle defines syllogism as "... A deduction in a discourse in which, certain things being supposed, something different from the things supposed results of necessity because these things are so." In modern times, this definition has led to a debate as to how the word "syllogism" should be interpreted. Scholars Jan Lukasiewicz, Józef Maria Bocheński and Günther Patzig have sided with the ProtasisApodosis dichotomy while John Corcoran prefers to consider a syllogism as simply a deduction.^{[4]}
In the third century AD, Alexander of Aphrodisias's commentary on the Prior Analytics is the oldest extant and one of the best of the ancient tradition and is presently available in the English language.^{[5]}
In the sixth century, the first translation of Prior Analytics by Boethius appeared in Latin. No Westerner between Boethius and Abelard is known to have read the Prior Analytics. Anonymus Aurelianensis III from the second half of the twelfth century is the first extant Latin commentary.^{[6]}
Contents 
The Prior Analytics represents the first formal study of logic which is the study of arguments; argument being in logic a series of true or false statements which lead to a true or false conclusion.^{[7]} In the Prior Analytics, Aristotle identifies valid and invalid forms of arguments called syllogisms. A syllogism is an argument consisting of three sentences: two premises and a conclusion. Although Aristotles does not call them "categorical sentences," tradition does; he deals with them briefly in the Analytics and more extensively in On Interpretation.^{[8]} Each proposition (statement that is a thought of the kind expressible by a declarative sentence)^{[9]} of a syllogism is a categorical sentence which has a subject and a predicate connected by a verb. The usual way of connecting the subject and predicate of a categorical sentence as Aristotle does in On Interpretation is by using a linking verb e.g. P is S. However, in the Prior Analytics Aristotle rejects the usual form in favor of three of his inventions: 1) P belongs to S, 2) P is predicated of S and 3) P is said of S. Aristotle does not explain why he introduces these innovative expressions but scholars conjecture that the reason may have been that it facilitates the use of letters instead of terms avoiding the ambiguity that results in Greek when letters are used with the linking verb.^{[10]} In his formulation of syllogistic propositions, instead of the copula ("All/some... are/are not..."), Aristotle uses the expression, "... belongs to/does not belong to all/some..." or "... is said/is not said of all/some..."^{[11]} There are four different types of categorical sentences: universal affirmative (A), particular affirmative (I), universal negative (E) and particular negative (O).
A method of symbolization that originated and was used in the Middle Ages greatly simplifies the study of the Prior Analytics. Following this tradition then, let:
a = belongs to every
e = belongs to no
i = belongs to some
o = does not belong to some
Categorical sentences may then be abbreviated as follows:
AaB = A belongs to every B (Every B is A)
AeB = A belongs to no B (No B is A)
AiB = A belongs to some B (Some B is A)
AoB = A does not belong to some B (Some B is not A)
From the viewpoint of modern logic, only a few sentences may be represented in this way.^{[12]}
Depending on the position of the middle term, Aristotle divides the syllogism into three kinds: Syllogism in the first, second and third figure.^{[13]} If the Middle Term is subject of one premise and predicate of the other, the premises are in the First Figure. If the Middle Term is predicate of both premises, the premises are in the Second Figure. If the Middle Term is subject of both premises, the premises are in the Third Figure.^{[14]}
Symbolically, the Three Figures may be represented as follows:
First Figure  Second Figure  Third Figure  

Predicate  Subject  Predicate  Subject  Predicate  Subject  
Major Premise  A  B  B  A  A  B 
Minor Premise  B  C  B  C  C  B 
Conclusion  A ********** C  A ********** C  A ********** C 
In the Prior Analytics translated by A. J. Jenkins as it appears in volume 8 of the Great Books of the Western World , Aristotle says of the First Figure: "... If A is predicated of all B, and B of all C, A must be predicated of all C."^{[16]} In the Prior Analytics translated by Robin Smith, Aristotle says of the first figure: "... For if A is predicated of every B and B of every C, it is necessary for A to be predicated of every C."^{[17]}
Taking a = is predicated of all = is predicated of every, and using the symbolical method used in the Middle Ages, then the first figure is simplified to:
If AaB
and BaC
then AaC.
Or what amounts to the same thing:
AaB, BaC; $therefore$ AaC ^{[18]}
When the four syllogistic propositions, a, e, i, o are placed in the first figure, Aristotle comes up with the following valid forms of deduction for the first figure:
AaB, BaC; therefore, AaC
AeB, BaC; therefore, AeC
AaB, BiC; therefore, AiC
AeB, BiC; therefore, AoC
In the Middle Ages, for mnemonic reasons they were called respectively "Barbara", "Celarent", "Darii" and "Ferio".^{[19]}
The difference between the first figure and the other two figures is that the syllogism of the first figure is complete while that of the second and fourth is not. This is important in Aristotle's theory of the syllogism for the first figure is axiomatic while the second and third require proof. The proof of the second and third figure always leads back to the first figure.^{[20]}
This is what Robin Smith says in English that Aristotle said in Ancient Greek: "... If M belongs to every N but to no X, then neither will N belong to any X. For if M belongs to no X, neither does X belong to any M; but M belonged to every N; therefore, X will belong to no N (for the first figure has again come about)."^{[21]}
The above statement is enormously simplified by using the symbolical method used in the Middle Ages:
If MaN
but MeX
then NeX.
For if MeX
then XeM
but MaN
therefore XeN.
When the four syllogistic propositions, a, e, i, o are placed in the second figure, Aristotle comes up with the following valid forms of deduction for the second figure:
MaN, MeX; therefore NeX
MeN, MaX; therefore NeX
MeN, MiX; therefore NoX
MaN, MoX; therefore NoX
In the Middle Ages, for mnemonic resons they were called respectively "Camestres", "Cesare", "Festino" and "Baroco".^{[22]}
Aristotle says in the Prior Analytics, "... If one term belongs to all and another to none of the same thing, or if they both belong to all or none of it, I call such figure the third." Referring to universal terms, "... then when both P and R belongs to every S, it results of necessity that P will belong to some R."^{[23]}
Simplifying:
If PaS
and RaS
then PiR.
When the four syllogistic propositions, a, e, i, o are placed in the third figure, Aristotle develops six more valid forms of deduction:
PaS, RaS; therefore PiR
PeS, RaS; therefore PoR
PiS, RaS; therefore PiR
PaS, RiS; therefore PiR
PoS, RaS; therefore PoR
PeS, RiS; therefore PoR
In the Middle Ages, for mnemonic reasons, these six forms were called respectively: "Darapti", "Felapton", "Disamis", "Datisi", "Bocardo"and "Ferison".^{[24]}
Figure  Major Premise  Minor Premise  Conclusion  Mnemonic Name 

First Figure  AaB  BaC  AaC  Barbara 
AeB  BaC  AeC  Celarent  
AaB  BiC  AiC  Darii  
AeB  BiC  AoC  Ferio  
Second Figure  MaN  MeX  NeX  Camestres 
MeN  MaX  NeX  Cesare  
MeN  MiX  NoX  Festino  
MaN  MoX  NoX  Baroco  
Third Figure  PaS  RaS  PiR  Darapti 
PeS  RaS  PoR  Felapton  
PiS  RaS  PiR  Disamis  
PaS  RiS  PiR  Datisi  
PoS  RaS  PoR  Bocardo  
PeS  RiS  PoR  Ferison 
"In Aristotelian syllogistic (Prior Analytics, Bk I Caps 47), syllogisms are divided into three figures according to the position of the middle term in the two premisses. The fourth figure, in which the middle term is the predicate in the major premiss and the subject in the minor, was added by Aristotle's pupil Theophrastus and does not occur in Aristotle's work, although there is evidence that Aristotle knew of fourthfigure syllogisms."^{[26]}
