The term "empirical" was originally used to refer to certain ancient Greek practitioners of medicine (Empiric school) who rejected adherence to the dogmatic doctrines of the day (Dogmatic school), preferring instead to rely on the observation of phenomena as perceived in experience. The notion of tabula rasa ("clean slate" or "blank tablet") dates back to Aristotle, and was developed into an elaborate theory by Avicenna and demonstrated as a thought experiment by Ibn Tufail. The doctrine of empiricism was later explicitly formulated by John Locke in the 17th century. He argued that the mind is a tabula rasa (Locke used the words "white paper") on which experiences leave their marks. Such empiricism denies that humans have innate ideas or that anything is knowable without reference to experience.
According to the empiricist view, for any knowledge to be properly inferred or deduced, it is to be gained ultimately from one's sense-based experience. As a historical matter, philosophical empiricism is commonly contrasted with the philosophical school of thought known as "rationalism" which, in very broad terms, asserts that much knowledge is attributable to reason independently of the senses. However, this contrast is today considered to be an oversimplification of the issues involved, because the main continental rationalists (Descartes, Spinoza, and Leibniz) were also advocates of the empirical "scientific method" of their day. Furthermore, Locke, held that some knowledge (e.g. knowledge of God's existence) could be arrived at through intuition and reasoning alone. Similarly, Robert Boyle, a prominent advocate of the experimental method, held that we have innate ideas.
Some important philosophers commonly associated with empiricism include Aristotle, Alhazen, Avicenna, Ibn Tufail, Robert Grosseteste, William of Ockham, Francis Bacon, Thomas Hobbes, Robert Boyle, John Locke, George Berkeley, David Hume, John Stuart Mill, Gilles Deleuze and Félix Guattari.