Empiricism - The Rise of Rationalism

Western thought was dominated by Aristotle's philosophy throughout the Middle Ages. But with the advent of the Scientific Revolution in the 16th century, Aristotelianism and it's empiricist account of knowledge was heavily challenged.

It is tempting to associate the rise of modern science with the success of observation and experience. But even more important than observation and experience was a new willingness to reject sensory experience as superficial and misleading. Modern science put a new emphasis on controlled experimentation and mathematics. This caused a profound realization that the world was often not what it appeared to be, which led to rationalism. It appears that the sun is orbiting the earth, yet Copernicus and Galileo proved the opposite to be true. In other words naïve observation got things backward.

As would be expected then, the three great philosophers of the early modern period were rationalists and not empiricists. They were Rene Descartes(1596-1650) Baruch de Spinoza(1632-77), and Gottfried Leibniz(1646-1716). They were impressed by the 'new sciences' and rejected Aristotelian empiricism while emphasizing the importance of abstract thought and deductive reasoning.

Rationalism - the idea that the world can only be known through reasoning and not experience - was given a new boost by the onset of modern science. Lets take an example of Descartes; the melting wax. In liquid form it has very different properties from a solid object. From sensory experience you know that it is different now, yet you judge it to be the same thing. What you know is the enduring object itself, and you know it with your intellect, not your eyes. What is called seeing is in fact judging. When I see a book lying on the table, am I seeing it? For Descartes(as for Plato) the answer would be no; what I see is a flux of shifting shapes and colors, and I think, 'This is a book'.

Descartes argued that we cannot acquire our ideas from sensory experience, because that would be like thinking that sound waves are actually travelling through telephone lines when we speak, when in fact the lines just relay electrical impulses that trigger the sounds of voices in telephones. So although many of our ideas seems to come from sensory experience, the ideas themselves already had to be in our minds in the first place. Descartes concluded that ideas were innate.

To sum up - The Scientific Revolution was driven by the rationalist principle that objects in the visible world are often not what they appear to be.

Source: The Bedside Baccalaureate