structural:reformatting
Reason compared to cause-and-effect thinking, and symbolic thinking

As pointed out by philosophers such as Hobbes, Locke, and Hume, some animals are also clearly capable of a type of " associative thinking ", even to the extent of associating causes and effects. A dog once kicked, can learn how to recognize the warning signs and avoid being kicked in the future, but this does not mean the dog has reason in any strict sense of the word. It also does not mean that humans acting on the basis of experience or habit are using their reason.

Human reason requires more than being able to associate two ideas—even if those two ideas might be described by a reasoning human as a cause and an effect—perceptions of smoke, for example, and memories of fire. For reason to be involved, the association of smoke and the fire would have to be thought through in a way that can be explained, for example as cause and effect. In the explanation of Locke, for example, reason requires the mental use of a third idea in order to make this comparison by use of syllogism.

More generally, according to Charles Sanders Peirce, reason in the strict sense requires the ability to create and manipulate a system of symbols, as well as indices and icons, the symbols having only a nominal, though habitual, connection to either (for example) smoke or fire. One example of such a system of symbols and signs is language.

The connection of reason to symbolic thinking has been expressed in different ways by philosophers. Thomas Hobbes described the creation of "Markes, or Notes of remembrance" as speech. He used the word speech as an English version of the Greek word logos so that speech did not need to be communicated. When communicated, such speech becomes language, and the marks or notes or remembrance are called " Signes " by Hobbes. Going further back, although Aristotle is a source of the idea that only humans have reason (logos), he does mention that animals with imagination, for whom sense perceptions can persist, come closest to having something like reasoning and nous, and even uses the word " logos " in one place to describe the distinctions which animals can perceive in such cases.