British Empiricism is a practical philosophical movement which grew up, largely in Britain, during the Age of Reason and Age of Enlightenment of the 17th and 18th Century. The major figures in the movement were John Locke, George Berkeley and David Hume.
Empiricism is the idea that the origin of all knowledge is sense experience. It emphasizes the role of experience and evidence, especially sensory perception, in the formation of ideas, while discounting the notion of innate ideas, and argues that the only knowledge humans can have is a posteriori (i.e. based on experience). It relies on induction or inductive reasoning (making generalizations based on individual instances) in order to build a more complex body of knowledge from these direct observations. Modern science, and the scientific method, is considered to be methodologically empirical in nature, relying as it does on an inductive methodology for scientific inquiry. See the section on the doctrine of Empiricism for more details.
Empiricism is usually contrasted with Rationalism (which holds that the mind may apprehend some truths directly, without requiring the medium of the senses), which became established in Continental Europe at around the same time, with the work of Descartes, Leibniz and Spinoza, among others. Locke, Berkeley and Hume vigorously defended Empiricism against these Rationalists.
The concept of a "tabula rasa" (or "clean slate") had been developed as early as the 11th Century by the Persian philosopher Avicenna, who further argued that knowledge is attained through empirical familiarity with objects in this world, from which one abstracts universal concepts, which can then be further developed through a syllogistic method of reasoning. Sir Francis Bacon can be considered an early British Empiricist, through his popularization of an inductive methodology for scientific inquiry, which has since become known as the scientific method.
However, the first explicit formulation of Empiricism was by the British philosopher John Locke in the late 17th Century. Locke argued in his "An Essay Concerning Human Understanding" of 1690 that the mind is a tabula rasa on which experiences leave their marks, and therefore denied that humans have innate ideas or that anything is knowable without reference to experience. However, he also held that some knowledge (e.g. knowledge of God's existence) could be arrived at through intuition and reasoning alone.
The Irish philosopher Bishop George Berkeley, concerned that Locke's view opened a door that could lead to eventual Atheism, put forth in his "Treatise Concerning the Principles of Human Knowledge" of 1710 a different, very extreme form of Empiricism in which things only exist either as a result of their being perceived, or by virtue of the fact that they are an entity doing the perceiving. He argued that the continued existence of things results from the perception of God, regardless of whether there are humans around or not, and any order humans may see in nature is effectively just the handwriting of God.
The Scottish philosopher David Hume argued that all of human knowledge can be divided into two categories: relations of ideas (e.g. mathematical and logical propositions) and matters of fact (e.g. propositions involving some contingent observation of the world, such as "the sun rises in the East"), and that ideas are derived from our "impressions" or sensations. In the face of this, he argued that even the most basic beliefs about the natural world, or even in the existence of the self, cannot be conclusively established by reason, but we accept them anyway because of their basis in instinct and custom. Hume's Empiricism therefore verges on Skepticism. John Stuart Mill took this reasoning a step further in the mid-19th Century in maintaining that inductive reasoning is necessary for all meaningful knowledge (including mathematics), and that matter is merely the "permanent possibility of sensation", as he put it.
In the late 19th Century and early 20th Century, developments stemming from British Empiricism also gave rise to several important movements including Pragmatism, Positivism and Logical Positivism.