<P> In the late renaissance various writers began to question the medieval and classical understanding of knowledge acquisition in a more fundamental way . In political and historical writing Niccolò Machiavelli and his friend Francesco Guicciardini initiated a new realistic style of writing . Machiavelli in particular was scornful of writers on politics who judged everything in comparison to mental ideals and demanded that people should study the "effectual truth" instead . Their contemporary, Leonardo da Vinci (1452--1519) said, "If you find from your own experience that something is a fact and it contradicts what some authority has written down, then you must abandon the authority and base your reasoning on your own findings ." </P> <P> The decidedly anti-Aristotelian and anti-clerical music theorist Vincenzo Galilei (c. 1520--1591), father of Galileo and the inventor of monody, made use of the method in successfully solving musical problems, firstly, of tuning such as the relationship of pitch to string tension and mass in stringed instruments, and to volume of air in wind instruments; and secondly to composition, by his various suggestions to composers in his Dialogo della musica antica e moderna (Florence, 1581). The Italian word he used for "experiment" was esperienza . It is known that he was the essential pedagogical influence upon the young Galileo, his eldest son (cf . Coelho, ed . Music and Science in the Age of Galileo Galilei), arguably one of the most influential empiricists in history . Vincenzo, through his tuning research, found the underlying truth at the heart of the misunderstood myth of' Pythagoras' hammers' (the square of the numbers concerned yielded those musical intervals, not the actual numbers, as believed), and through this and other discoveries that demonstrated the fallibility of traditional authorities, a radically empirical attitude developed, passed on to Galileo, which regarded "experience and demonstration" as the sine qua non of valid rational enquiry . </P> <P> British empiricism, though it was not a term used at the time, derives from the 17th century period of early modern philosophy and modern science . The term became useful in order to describe differences perceived between two of its founders Francis Bacon, described as empiricist, and René Descartes, who is described as a rationalist . Thomas Hobbes and Baruch Spinoza, in the next generation, are often also described as an empiricist and a rationalist respectively . John Locke, George Berkeley, and David Hume were the primary exponents of empiricism in the 18th century Enlightenment, with Locke being the person who is normally known as the founder of empiricism as such . </P> <P> In response to the early - to - mid-17th century "continental rationalism" John Locke (1632--1704) proposed in An Essay Concerning Human Understanding (1689) a very influential view wherein the only knowledge humans can have is a posteriori, i.e., based upon experience . Locke is famously attributed with holding the proposition that the human mind is a tabula rasa, a "blank tablet", in Locke's words "white paper", on which the experiences derived from sense impressions as a person's life proceeds are written . There are two sources of our ideas: sensation and reflection . In both cases, a distinction is made between simple and complex ideas . The former are unanalysable, and are broken down into primary and secondary qualities . Primary qualities are essential for the object in question to be what it is . Without specific primary qualities, an object would not be what it is . For example, an apple is an apple because of the arrangement of its atomic structure . If an apple was structured differently, it would cease to be an apple . Secondary qualities are the sensory information we can perceive from its primary qualities . For example, an apple can be perceived in various colours, sizes, and textures but it is still identified as an apple . Therefore, its primary qualities dictate what the object essentially is, while its secondary qualities define its attributes . Complex ideas combine simple ones, and divide into substances, modes, and relations . According to Locke, our knowledge of things is a perception of ideas that are in accordance or discordance with each other, which is very different from the quest for certainty of Descartes . </P>

Philosopher who developed formal logic and the philosophy of empiricism