A close study of these relations, and the symbols expressing them, is necessary for a clear comprehension of the Laws of Opposition stated a little further back, as well as the principles of Conversion which we shall mention a little further on. The following chart, called the Square of Opposition, is also employed by logicians to illustrate the relations between the four classes of propositions: A CONTRARIES E +------------------------+ |\ / | | \ /S | | C\ /E | | O\ /I | | N\ /R | | T\ /O | S| R\ /T |S U| A\ /C |U B| \ /I |B A| \ /D |A L| \ / |L T| / \ |T E| / D\ |E R| / I\ |R N| /A C\ |N S| /R T\ |S | /T O\ | | /N R\ | | /O I\ | | /C E\ | | / S\ | |/ \ | +------------------------+ I SUB-CONTRARIES O _Conversion_ is the process of immediate reasoning by which we infer from a given proposition another proposition having the predicate of the original for its subject and the subject of the original for its predicate; or stated in a few words: _Conversion is the transposition of the subject and predicate of a proposition_. As Brooks states it: "Propositions or judgments are _converted_ when the subject and predicate change places in such a manner that the resulting judgment is an inference from the given judgment." The new proposition, resulting from the operation or Conversion, is called the Converse; the original proposition is called the Convertend. _The Law of Conversion_ is that: "No term must be distributed in the Converse that is not distributed in the Convertend." This arises from the obvious fact that nothing should be affirmed in the derived proposition than there is in the original proposition. There are three kinds of Conversion; _viz_: (1) Simple Conversion; (2) Conversion by Limitation; (3) Conversion by Contraposition. In _Simple Conversion_ there is no change in either quality or quantity. In _Conversion by Limitation_ the quality is changed from universal to particular. In Conversion by Negation the quality is changed but not the quantity. Referring to the classification tables and symbols given in the preceding pages of this chapter, we may now proceed to consider the application of these methods of Conversion to each of the four kinds of propositions; as follows: