According to Aristotle, the first figure is the perfect figure because the validity of the moods of this figure can be directly tested by a principle which is self-evident. This principle is known as the Dictum de Omni et Nullo. It literally means ‘a statement concerning all and none’. The Dictum states that ‘what is said of All or None may be said of anything contained therein’.
The dictum can be expressed as follows:
What ever is affirmed or denied of a whole class may be affirmed or denied of everything contained in that class.
The same principle has also been stated in the following manners.
Whatever is predicated (affirmed or denied) universally of any class of things, may be predicated in the like manner (affirmed or denied) of anything comprehended in that class.
The dictum can be analysed into three parts (in the form of a syllogism).
1. Anything whatever predicated of a term distributed. (The major premise).’ All or No M is P’.
2. Under which term something else is contained. (The minor premise ‘S is M’).
3. May be predicated (in the like manner) of that which is so contained. (The conclusion) S is P.
We can illustrate the application of the dictum with the help of some examples.
1. All children are inquisitive.
Sweta is a child.
Therefore, Sweta is inquisitive.
2. No man is perfect.
Sushant is a man
Therefore, Sushant is not perfect.
In the first example, we attribute the quality of being inquisitive to all children. In the minor premise, we affirm that Sweta is a member of the class ‘children’.
In the conclusion, by applying the rule, we affirm that Sweta is inquisitive. Likewise, in the second example, perfection is denied of the whole class of men. The minor premise (Sushant is a man) affirms that Sushant is included in the class of man. In the conclusion, the quality of being perfect is denied of Sushant who is a member of the class ‘man’.
We notice that in the above examples the major premise is universal, the minor premise is affirmative and the quality of the conclusion is determined by the quality of the major premise Notice that these are the special features of the first figure.
We can notice that the principle directly applies only to the first figure of syllogism. In the first figure the pattern of argument is that some general rule is applied to a particular case. The major premise states a general principle, (either affirmative or negative) the minor premise entry that some particular case comes under this principle and the conclusion applies the general principle to the particular case.
Thus the dictum directly applies to the valid modes of the first figure (BARBARA, CELARENT, DARII and FERIO). So the first figure is regarded as the perfect figure. The other figures are said to be imperfect figures from the standpoint of Aristotle’s dictum.