Square of Opposition

Introduction Square of opposition:

In this article We shall see about square of opposition.Square of opposition means that the  collection of logical relationships traditionally represented  in a square diagram.In another way,We define that the Square of Opposition is normally defines the logical relationship between the many of the proposition.It is not similar to predicate calculus.This is entirely different.The square of opposition is mainly used in the modern time calculus.
Square of Opposition Explanation - Square of Opposition

The square of opposition looks likes as given below.It will represent the logical relationship between the premises in an real world manner.Its likes an squared chart.so that this is called as square of opposition.

Square of opposition Diagram:

square of opposition

The four edges of this square of opposition chart will represent the four basic forms of propositions or premises  recognized in the classical logic,

A propositions :

The title for this is universal affirmatives .

It will be represented in the form: All S are P.
E propositions:

The title for this is  universal negations .

It will  be repesented in the form: No S are P.
I propositions:

The title for this is  particular affirmatives .

It will be repesented in the form: Some S are P.
O propositions:

The title for this is particular negations.

It will be repesented in the form: Some S are not P.
Square of Opposition Examples:

From the given  chart  the assumption made within classical categorical logic, that every categoryin the squre of opposition graph  contains at least one member. Classical categorial logic is also called as Aristotelian logic.The following relationships, are found in the square of opposition chart.


From the Diagram we understood that, A and O propositions  and  E and I propositions are contradictory.When the truth of one proposition specifies that  the false of the other proposition, and also in conversely then that Propositions are said to be contradictory

Here we see that the truth of a proposition of the form All S are P implies that the false of the corresponding proposition of the form Some S are not P.

Example 1:

If the proposition “All human respect the educated peoples” (A) is true, then the proposition “some human not respect the educated peoples” (O) must be false.

Example 2:

Similarly, if “no one is bad” (E) is false, then the proposition “some one is good” must be true.


From the above diagram we understood that  A and E propositions are contrary. Propositions are said to be contrary when there is no possibility for that cannot both be true.

Example 3:

An A proposition,  “all humans have 6 fingers” is not be true at the same time as the corresponding E proposition: “no human have 6 fingers.” is not true.

Example 4:

“All Vehicles create the pollution”  is not true and “No Vehicles create the pollution” is also not true


From the above diagram we understoosd that I and O propositions are said to be subcontrary. Propositions are said to be subcontrary when there is no possibility  for both to be false.

Example 5:

The following statements are in sub contrary relation.. “some one is bad” is false, “some one is not bad” must be true.

Example 6:

As with “some nations are democracies,” and “some nations are not democracies.” The I and O propositions aresaid to be subcontrary, but not contrary or contradictory.


The truth of the first (“the superaltern”) specifies  that  the truth of the second (“the subaltern”)  but not conversely then  Two propositions are said to be  in the relation of subalternation . A  propositions  relation in the chart  stand in the subalternation relation with the corresponding I propositions relation.

Example 7:

The truth of the A proposition “All humans likes icecream,” implies the truth of the proposition “some humans likes icecream.”

However, the truth of the O proposition “some mobiles are not china-made products” does not imply the truth of the E proposition “no mobiles are China-made products.”

Modern square of opposition:

In the above classical logic, the truth of an  proposition A or E in chart shows   that the truth of the corresponding related proposition I or O , respectively. Likewise, the falsity of an I or O proposition in an chart implies that the falsity of the corresponding A or E proposition in an chart respectively. What ever, the truth of a specific  proposition in an chart does not imply  that the truth of the related universal proposition in an chart , nor does the falsity of an universal proposition carry downwards to the respective particular propositions.

The supposition that all categories in an square  must have the  at least one member according to the modern square of opposition, then only the contradictory relation holds between them. So that the lines in squares for contraries, subcontraries and subalternation are deleted  in  “modern square of opposition”  ,and then  allowing only the diagonal lines for the above contradictory relation.

modern square of opposition