Arguments on the LSAT often draw a conclusion based on the premise that there is a limited set of options. However, these arguments can sometimes make a wrong turn along the way. The fallacy of exclusivity takes two forms:
1. Fails to establish the list of options is exhaustive (that no other option is available) or an argument will fail to sufficiently eliminate some of the options; and
2. Falsely assumes that two options are exclusive (that it cannot be some combination of both).
Arguments sometimes make conclusions about a whole entity from evidence about its parts, or vice versa. Fallacies of composition occur when the author assumes that the whole is nothing more than the sum of its parts. When elements are joined together in a while, that whole makes take on different properties than any of those parts possessed. Conversely, it may lack properties that some or even all the parts possessed.
Two Common Flaws of Composition
1. From the fact that a whole has a certain property, it is concluded that all/most/some of its parts must have it as well.
2. From the fact that one/most/all of the parts have a certain property, it is concluded that the whole must have this property.
Sufficiency and Necessity
1. Fallacy of the converse
A->B therefore B->A
2. Fallacy of the Inverse
A->B therefore /A->/B
The fact that one thing implies another is not sufficient to prove that the first thing causes the second. The burden of proof is so high for cause and effect relationships that causal conclusions are rarely valid.
Correlation does not imply causation. The fact that A always implied B, or that A and B always imply each other, is insufficient to conclude that A must cause B.