Subject: Do We Want to Talk about the "Purpose" behind the Change?

Posted by Ford, Andy on 2/9/2006

Message:

Folks,



This is Andy Ford responding to Jeff Levin's suggestion:



Maybe Professor Forrester's statement should be changed to say:

"Everything that changes purposefully through time is controlled by feedback

loops."



Jeff went on to say that: “There would have to be a purpose behind the change.”



I’ve highlighted “purposefully,” the new word that Jeff would add to Forrester’s statement about feedback loops. My feeling is that Forrester’s original statement stands on its own. (I am still scratching my head, searching for a counter example.) I believe the addition of the word “purposefully” would lead us away from a discussion of the closed chain of cause and effects which we call “feedback.” If we start attempting to define whether there is “purpose behind the change”, we will reveal much more about our philosphical views of the world than about our concrete understanding of the cause and effect relationships in that world. I’ll illustrate with two examples:



Home Heating System:

First, we probably all use the example of a home heating/cooling system in our classroom. The operation of the furnace and the air conditioning is controlled by a target temperature set by a thermostat. We all see the feedback in the system – lower indoor temperatures trigger the furnace to run more frequently and warm the house, for example. There definitely seems to be “purpose behnd the change” when the furnace comes on.



Daisy World:

Now consider the Daisy World parable invented by James Lovelock and Andrew Watson to illustrate the “Gaia Hypothesis.” The Gaia idea is that the living and nonliving parts of the world interact in a way to be condusive to life on the planet. Laurince Levine writes of the Gaia idea as in effect, the whole earth follwing the homeostatic principles first put forth by the physiologist Walter Cannon (in his wonderfull book on The Wisdom of the Body) – “according to Gaia, the rocks, grass, birds, oceans and atmosphere all pull together, act like a huge organism to regulate conditions.” This type of thinking sounded too much like teleology to mainstream biologists who argued that “nature does not think ahead or behave in any kind of purpseful manner” These critics, in turn, were attacked by others as being too narrow minded to see that “life on Earth could create and regulate the conditions for its own existence without being conscious and purposefull.”



Daisy World was invented to sort through these views with a concrete example. It is a make believe planet occupied by only two types of plants – white daisies and black daisies. The white daisies have high albedo and reflect a lot of the incoming solar luminosity; the black daisies absorb much more of the incoming luminosity. The spread of the Daisies across the surface of the world influences the temperature of the planet, and the growth of the daisies is dependent on temperature. The world exhibits a remarkable property of controlling temperature in the face of massive changes in the incoming solar luminosity. Clearly, we would all agree that there are feedback loops in this system. But, would we agree that there is “purpose” behind the change? After all, the parable of Daisy World was created to counter the view of mainstream biologists who argue that nature does not act in a purposefull manner.



Andy Ford

Professor

Program in Environmental Science

Washington State University

Pullman, WA 99164-4430



FordA@mail.wsu.edu

Follow Ups:

Do We Want to Talk about the - John Gunkler 2/9/2006 
Do We Want to Talk about the - Richard Turnock 2/25/2006
Do We Want to Talk about the - Ashis Sen 2/25/2006
Do We Want to Talk about the - Jay W. Forrester 2/17/2006
Do We Want to Talk about the - Ashis Sen 2/25/2006
Do We Want to Talk about the - Michael Round 2/19/2006
Do We Want to Talk about the - Jay W. Forrester 2/25/2006
Do We Want to Talk about the - Louis Macovsky 2/27/2006
Do We Want to Talk about the - Louis Macovsky 2/25/2006
Do We Want to Talk about the - Louis Macovsky 2/27/2006