Science and Consensus

Image from http://www.negotiationlawblog.comImage from

Writing about the nature of belief in reference to science  the other day started me thinking about other specific issues I have encountered in discussing science with non-scientists.  Coffee also helped this endeavor.

Something I hear in discussion a lot, especially about topics such as climate change and evolution, is the following: “Yeah, well, I read an article by this one guy who says that X is/isn’t true.  I thought you were all in agreement?  I guess you really don’t know, then, do you?”  You’ve probably encountered this argument before as well.  Really, it can be broken into two pieces that can be addressed individually: the consensus problem and the knowing problem.  I’ll address the first today and the second in a later post.

The Consensus Problem

The whole “I though you were all in agreement” statement falls apart once you understand that empirical knowledge is not a consensus.  In order for a scientific theory to be considered “true”, or more accurately, for it to be considered the working model of a phenomenon, what is required is that the presented theory fits the observed facts.  Can there be more than one model?  Sure, it happens all the time.  However, as more and more data is collected, the observations give more credence to one of the models at the expense of the others.  Scientific consensus is established when a model shows that it more closely represents reality than the alternatives.

Take the example of the theory of plate tectonics, the idea that the Earth’s crust is fractured into many smaller plates that float around on the warm, chewy nougat mantle due to the convection of heat between the hot core and the cooler surface.  When the theory was first presented at the beginning of the 20th century, no one really took it seriously.  How could the continents drift?  That’s absurd!  In the beginning, the “motor” of convection wasn’t known.  But, similarities in fossils and a variety of geologic features seemed to point to the idea that at sometime in the past, the continents were all mashed together and then somehow broke apart and moved to their present locations.  Over the years, more and more data was presented to support the idea; the discovery of the mid-ocean ridges, the magnetization of rock samples separated by thousands of miles, the obvious jigsaw-like coastlines of the continents themselves.  Eventually, a majority of the scientific community could no longer deny that plate tectonics was the preferred model and every aspect of earth science changed.

Now, did the entire scientific community just up and decide that the theory was correct in a magical moment when every single earth scientist just said, “Yes. Plate tectonics is the way”?  No.  Indeed there was, particularly in the 1950’s and 1960’s, fierce debate over its validity.  There are probably a few outliers today that still do not accept the theory.  But, science chose the model that fit Nature.

Another possible outcome here is that one of the theories turns out to be a special case of something greater.  When Einstein presented the General Theory of Relativity, a new take on the force of gravity and the nature of space and time, the established framework of Newtonian mechanics became a subset of that theory.  Newtonian mechanics made all sorts of assumptions that, it turned out, were false.  In our every day experience, we would never notice these errors; Newtonian mechanics is a fantastic description of everyday motion.  However, go to the scale of interstellar space and it just isn’t enough to describe what we see.  Indeed, general relativity was born from the inability of Newtonian mechanics to explain how Mercury orbits the Sun, along with other observed gravitational “errors”.  Again, it’s all about whether or not the theory explains the observed details, not whether every single person agrees with it.  Needless to say, Einstein’s overthrow of 300 years of theory from Newton did not go over well in the beginning.  But, as with plate tectonics, scientists eventually acquiesced that general relativity was a better model, it more closely fit nature.

My point here is this: a scientific model does not require consensus to be accurate.  It doesn’t need to fit the belief structure of those observing it.  It only needs to fit the observed data.  Say you are teaching a science lab at a high school.  You give each of your 40 students an identical cube of metal and ask them to find out what it is by calculating its density.  Thirty-nine of them tell you it’s iron but one says it’s silver.  What conclusion should we draw from this?  That the concept of density is somehow flawed because not every single person agrees?  Hardly…

In a later post, I will discuss the knowing problem, an issue with deeper philosophical roots, I suppose.  Until then, I’ll brew some more coffee.


  1. Jen

    Great topic baby! I’m glad you addressed it. It’s so annoying when people think science is a unanimous decision or something.

  2. Pingback: The Knowing Problem |

  3. For some reason, this got me thinking about revisionism in history and how everybody believes that Abraham Lincoln had a deep voice.

    1. kdavenport

      I know, right?

Leave a Reply

Your email address will not be published. Required fields are marked *