Syllogism

Syllogisms are a type of logical reasoning often used in philosophical arguments. Logical reasoning involves abstract thinking: you approach a problem by organizing a series of steps (called premises) into a particular order.

Syllogisms are the most common way of arranging premises into a good argument. A syllogism is a form of deductive argument where the conclusion follows from two (or more) premises that are known to be true. A deductive argument moves from the general to the specific and opposes inductive arguments that move from the specific to the general.¹ Here’s an example of a basic syllogism that follows this structure:

1. All mammals are animals.
2. Camels are mammals.
3. Therefore, camels are animals.

As long as “premise one” and “premise two” are true, then the conclusion must also be true. If mammals are animals, and camels are mammals, there is no way camels aren’t animals! As stated, syllogisms typically have three parts—two premises and a conclusion—although “syllogism” is sometimes used to refer to any deductive argument.

The first statement is called the major premise, and the second is the minor premise. Universal syllogisms, like the one above, use all-encompassing terms such as “all” or “only.” Particular syllogisms, on the other hand, are framed differently.² For example:

1. No humans are immortal.
2. Some organisms are immortal.
3. Therefore, some organisms aren’t humans.

However, it’s only when both premises are proven true that the argument is considered sound. A syllogism may state that all birds can fly, penguins are birds, and therefore, penguins can fly. Though the argument is logically structured, it includes a false premise (all birds can fly), making the argument unsound.