Although there are many different classifications of philosophical problems, the division of philosophy into ontology (or metaphysics), epistemology, and axiology (ethics and aesthetics) still seems the most efficient and general one. Thus, epistemology belongs to the main parts of philosophy. However, the terms which now denote this field, namely "epistemology' and "theory of knowledge', appeared not very long ago, later than terms indicating metaphysics, ethics, aesthetics or even ontology. As late as in the 17th century there was no single word referring to epistemology. At that time as well as in the 18th century, epistemological problems were considered in books like (I give the English titles) Rules for the Direction of Mind (René Descartes), An Essay Concerning Human Understanding (John Locke), A Treatise Concerning the Principles of Human Knowledge (George Berkeley), An Enquiry Concerning Human Understanding (David Hume), New Essays on Human Understanding (Gottfried Leibniz) or Critique of Pure Reason (Immanuel Kant). Kant placed his central epistemological views under the label "transcendental aesthetic', following the meaning of aisthesis as referring to cognition by senses. As a matter of fact, Kant also used (in his Critique of Aesthetic Judgement) the term "aesthetics', more precisely, its German counterpart Aesthetik, in a more contemporary fashion, i.e., to denote matters of beauty. Earlier, Alexander G. Baumgarten in his Sciagraphia encyclopaediae philosophicae (1769) proposed the word gnoseologia,which gained some popularity and is sometimes employed even now. The German word "Erkenntnistheorie' (theory of knowledge) became popular after Eduard Zeiler's influential paper "Bedeutung and Aufgabe der Erkenntnistheorie" (1862), but this name and its cognates were used earlier. Thomas Krug's, Allgemeine Handwörterbuch der philososophischen Wissenschaften (1827) proposed the label "Erkenntnislehre'. Ernst Reinhold (the son of Karl L. Reinhold, a leading post-Kantian philosopher) in Versuch einer neuen Theorie der menschlichen Vorstellung-svermögen and Metaphysik (1832) had the term "Theorie der Erkenntnis". It was James E Ferrier who introduced the label "epistemology' in his Institutes of Metaphysics (1854). Other words were also proposed to baptize our field: Wissenschaftslehre' (Johann G. Fichte, Bernard Bolzano), Wissenschaftstheorie' (Eugen Dühring), "criterology' (Neo-Thomists), and "noetics' (also NeoThomists). However, the words "epistemology' and "Erkenntnistheorie' (as well as their translations into other languages) are most popular nowadays.