ABSTRACT
We can establish the validity of an argument by showing explicitly how the premises can be interwoven to obtain the stated conclusion. The premises can be manipulated (taken apart or conjoined) through a series of intermediate steps, each of which is justified by citing a specific Rule of Inference. Each such rule provides a legitimate inference or rephrases a statement in a logically equivalent form. Such a formal demonstration is termed a derivation. We will look at three particular techniques used in constructing derivations: direct proofs, indirect proofs, and the method of mathematical induction. Also, we introduce the derivation graph, which provides a visual representation of the internal structure of an argument.
