Deductive arguments are based upon multiple premises or facts to infer a conclusion from those premises. A deductive argument is valid if the concluding statement from those premises has no other option but to be true. If the concluding statement and premises allow for the concluding statement to have a chance of being false, then the deductive argument is invalid. It should be noted that the premises in a deductive argument can be false, but the argument can still be valid as long as the premises ensure the conclusion is correct. If the premises or conclusion are false, then the deductive argument is labeled not sound.
An example of a valid deductive argument would be:
The Oilers will win the game if they score more goals than the Flames. The Oilers scored more goals than the Flames in the game. Therefore, the Oilers won the game.
An example of an invalid deductive argument would be:
All sailboats have a sail. Sailfish have a sail. Therefore, a sailfish is a sailboat.
One type of common fallacy is a ‘fallacy of composition’. This type of fallacy occurs when a truth is said about a part of a particular object or entity and then applied to the whole object as being a truth when it is actually false. This is a fallacy because the argument being applied is if part of something about that entity is true, then it must be true from the rest of the entity, which can be false.
An example of a fallacy of composition would be:
A house’s door is red. Therefore, the whole house is red.
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