\begin{definition}[Definition:Reduction to First Figure/Indirect]
'''Indirect reduction to the first figure''' is a form of the reduction to the first figure method for determining the validity of a categorical syllogism.
This form of the method works backward by supposing that a pattern is not valid, and then deriving a contradiction against a known valid pattern in the first figure.
Hence by Reductio ad Absurdum the pattern is deduced to be valid.
\end{definition}