[Partly edited 9/21/11 and 9/19/12]



The 17th century was a time of incredibly rapid change and a great deal of uncertainty.  Everything taken for granted in earlier times had changed, was changing, or was about to change.  It's uncomfortable to live in such times.  We want certainty!  One playwright (Maurice Maeterlink I think) has a line about such uncertainty, "Not to know where one is, where one has been, not to know where one is going: I would rather not live."  Not surprisingly, the great thinkers of the 17th century turned their minds to task of providing certainty, trying to show how one could know that certain things were true.  Foremost among them: Bacon, Descartes, and Pascal.  These men did an excellent job in suggesting ways one might effectively pursue truth and certainty, and each of them did quite a bit to provide order and assurance amid the uncertainties of the 17th century.


 When we claim we "know" something, what are the possible sources of that knowledge?  Here are some possibilities:

 --Authority (we get our knowledge from an expert)
 --Experience (we get our knowledge from things we personally see, taste, touch, smell)
 --Reason  (we get our knowledge through logic)
 --Revelation (we get out knowlege from some transcendent source)
 --Innate (we are born with knowlege)

Which of these is most important?  Most of the time, we resort to authority. If we want to know the speed of light (299,792.458 kilometers per second), we want to just look in a textbook: we don't want to replicate the Michelson-Morley experiements ourselves!   But relying on authority wasn't sufficient in the 17th century.  Why?  In just about every area, whether in astronomy, physics, medicine or religion, the authorities simply did not agree.  Who was the "authority" in each of these areas? 

It's not suprising, then, that in and attempt to get back on a stable footing, 17th century thinkers begin to look beyond the established authorities as the primary source of knowledge.  So where do you look?  One obvious source of knowlege: our own experience--if we use that experience correctly.  Important in suggesting just how we might use our own experience to increase our knowlege of the world: the English writer Sir Francis Bacon.


You can identify Sir Francis Bacon (1561-1626) and an English writer, diplomat, and philosopher. He wrote a tremendously important book, "Novum Organum"--the new instrument (or, "the new method").  In this book, Bacon champions the use of what we call inductive reasoning, using experience as our source of knowledge.  This alone, of course, is not particularly new.  What is new is the advocacy of a more systematic use of experience, the experimental method, what we call scientific method.

If we are to interpret our experience correctly, warns Bacon, there are certain things we have to avoid, what Bacon calls "idols."  These idols are of four sorts as follows:

1.  The Idols of the Tribe.  These are our physical limitations as human beings.  Because we're humans, the sun appears much smaller than it is.  We don't see all wave lengths of light.  Learning from experience does *not* mean to just assume that everything is as it appears to be!

2.  The Idols of the Den or Cave.  Our own previous experiences tend to color our understanding and sometimes mislead us.  We must get rid of such prejudices and be willing to challenge our old ideas if we are to arrive at truth.

3.  The Idols of the Marketplace.  Our search for truth can be made harder by confusion in the way we exchange our ideas.  The exchange of ideas with others may lead to circulation of false ideas.  In particular, have to watch out for the medium of exchange, words.

4.  The Idols of the Theater.  Just as actors can make pretense seem reality, so our "great" thinkers can make false or inaccurate concepts seem like reality.  The great philosophic systems in particular (like the medieval synthesis of knowledge I talked about) especially create an illusion of knowlege by giving us a majetic spectacle.  Such systems may make false ideas extremely attractive to us and hard to challenge.

Freed from idols, experience can guide us to truth. We become ready to challenge the great philosophic systems.  Instead, we break down subjects into fields and subfields, and then examine each topic on its own merits.  Bacon himself suggests how we ought to go about this in his investigation of heat.  First, he lists all sources of heat.  These include:
Examining these, we see that heat is not caused by any of the following:

What do all hot objects have in common?  Movement of some sort--and Bacon concludes that heat  is essentially movement: the right answer!

Note that such systematic treatment eventually does produce not merely a plausible answer, but an answer one can have considerable confidence in.  Bacon predicted that such systematic examination of nature would greatly increase knowledge and make lives better, and, as Bacon's method has been applied through the years, it has done what he thought it would.  It has led to a better understanding of physics, biology, geology, etc. 

But there one problem.  Bacon's method works well for sciences.  But what about things we really care about?  If you were to have answer to any one question, and were certain to get the right answer, what would your question be? It's far more likely that your question would concern great philosophical, religious, or interpersonal issues--not questions about the material world.  Unfortunately,  Bacon's method is no good for such things, and so it's not surprising that other great 17th century thinkers suggested different approaches for gaining knowledge and certainty. One such: Rene Descartes who we will talk about  next time.