Cogito ergo sum (I think therefore I am). These words of Descartes sum up the importance of thought processes in humans and probably the most important reason we differ from animals. Although animals retrieve and store information, there is little evidence to suggest that they can use it in quite the same way as humans. Humans, on the other hand, are able to use information to reason and solve problems, even when the information is partial or unavailable.

Thinking can be categorized into reasoning and problem solving. Although these are not distinct they are helpful in clarifying the processes involved.