Every Formal Logic relationship features at least two separate variables linked in a relationship. The
variables represent groups or ideas. For instance, in the example on the previous page, “A” represented
“authors” and “H” represented “happy.” These variables—and LH and F—were linked in relationships
that were represented by the diagrammatic elements of “some,” “---> ,” and “<---> .” Below, we
discuss the components of Formal Logic diagrams in more detail.
1. Choosing Symbols to Represent Each Variable
Choosing symbols to represent each group or idea is easy: simply choose the letter or letters that, to you,
best represent the element. For most people, the best symbols are the first letter of each word or words. For
example, using “A” to represent “authors” makes it easy to remember “authors” when you are examining
your diagram. The exact letters you choose to represent each group are not critical; what is important is
that you use those same letters to represent the group throughout your diagram and inferences. This is
especially important as some terms are negated. For example, if you represent “happy” with “
begin your diagram, and later you are presented with a seemingly new element, “unhappy,” do not create a
new variable, “UH.” Instead, simple negate “happy” and use “ H .”
2. Conditional Reasoning Terms and Diagrams
Many of the relationship indicators used within Formal Logic problems are terms you are familiar with
from Conditional Reasoning. Conditional indicators such as “if” and “only” yield exactly the same
diagrams that you used in Sufficient and Necessary problems. Let us briefly review those terms and their
resultant diagrams:
