Epistemology is a branch of philosophy that focuses on nature, sources, limitations, and criteria of knowledge.

Epistemological Questions

In the process of acquiring knowledge, two basic questions of epistemology are revealed. The first question is how can we know something? If we assumed that the world is as we perceive it through our senses, we would not know reality because of visual, acoustic, and other deviations. Another way of knowing the true nature of things is reason. Reason, however, can be influenced in the same way as perception by several factors like forgetting, misinterpretations and hasty conclusions. What happens if the knowledge we gain through reasoning contradicts our perceptions? This raises two further questions: Is reality independent from our sensual perceptions, and how can we know what is real if our perceptions contradict each other?
The second main epistemological question relates to the psyche of the other. As it seems impossible to know what goes on in the mind of other people, we can conclude that no one can know what other people are thinking. As a result, our perceptions of the minds and experiences of others can only be based on our observations of their condition and behavior.
In the field of epistemology, these questions have led to different conclusions. Since things are not what they seem to be at first, it is necessary to differentiate between outer appearance and the real world. This is the classic philosophical difference between appearance and reality.
Consequently, the term knowledge has to be defined and the relevant relationship between knowledge and perception has to be investigated. In the course of this investigation, a determination must be made as to how far perception influences our knowledge.

Sources of knowledge

The research on the sources of knowledge has always been one of the most important topics of epistemology. In the course of time, two main theories have emerged. Rationalism names reason as the only source of knowledge. This implies that reality can be captured in principle and that we have the mental capacity to do so. Empiricism, in contrast, maintains that sensual perceptions are the only source and the ultimate touchstone of knowledge. The history of epistemology is, for the most part, an interaction between rationalism and empiricism, especially when dealing with skeptics who try to undermine both positions.


Skeptics doubt that we are able to acquire knowledge of truth and reality at all. They argue that there is always a difference between outer reality and our sensual perceptions. As a result, one cannot verify claims made on these perceptions. Skeptics do not question knowledge itself; they only question the claim that knowledge in this sense is possible.




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Designed by Karen Hoehnke, Veronika Koch und Ulrike Lutz.

Translated by Nina Burr, Irina Haas, Andrea Kühn, Oliver Müller, Thea Roll, Sabine Ruflair and Mareike Zeller.
Last updated January 30, 2003