If you have take a formal logic course, you will recognize this as the logical fallacy of “affirming the consequent“. The LSAT test designers recognize it as a tool to attract you to the wrong answer.
Sometimes a picture is worth a thousand words. Here is a nice picture that explains why bad backward reasoning is bad. Hat tip to “LSAT Freedom”.
— LSAT PREParation (@LSATPreparation) July 8, 2013
— LSAT Freedom (@LSATFreedom) July 7, 2013
Bad backward reasoning is one of many components taught in university logic courses. It is an aspect of the proper understanding of “conditional statements”. Listen to my interview of Professor D. Bennet about her book “Logic Made Easy“.