What do you think of when you hear the term “science”?  White lab coats?  Microscopes and Bunsen burners?  STEM?  While all of these relate to science, perhaps its most basic feature is observational evidence.  Afterall, it is observational evidence that scientists gather in the natural environment, labs, and clinical trials.  

Now, what if science, at its core, relied on a fundamental assumption about nature that wasn’t supported by observational evidence?  And what if this was the case and scientists rarely, if ever, discussed it?  Finally, what if this assumption was the basis for life-and-death medical decisions, technological development, and a host of other choices?

As it turns out, science does rely on such an assumption and its existence reveals an important truth about science that can be easily overlooked.  This assumption, which is held by every scientist (consciously or subconsciously), is that the patterns witnessed in nature under specific conditions will continue to occur when these conditions are present at other times and places.  This assumption is referred to commonly as the “uniformity of nature”.  Put in more practical terms, it is the assumption that what the scientist observes at specific times and places under specific physical or experimental conditions is an accurate representation of what would be observed at any time or place where those same conditions are present.  It is fundamental because it allows scientists to extend their research findings beyond their observations, apart from which general scientific knowledge would be impossible.  Ultimately, any science-based decision in any field (e.g. medicine, chemistry, physics, etc.) rests on this fundamental assumption.

Given the value of observational evidence in science, it would seem that this assumption of nature’s uniformity should itself be supported by observational evidence.  Following the hypothetical reasoning of the famed philosopher David Hume, we can imagine an argument that goes something this:  Nature has behaved uniformly when observed in the past and in different places and, therefore, nature will always behave uniformly.  At first glance, this may seem reasonable.  However, as Hume and others have indicated, this type of argument presupposes the truth of the conclusion.  In other words, without presuming that nature will always behave uniformly, how could one ever be sure that their limited observations of uniformity were representative of all of nature?  The upshot is that there is no way to establish the truth of this assumption using observational evidence.  There is, therefore, an “evidence paradox” in science, in which observational evidence is simultaneously esteemed and yet unable to justify this key assumption about nature. 

The evidence paradox points to an important truth: science must look outside of itself for justification.  The humanities, such as philosophy, are required to more fully understand science and how it is capable of yielding knowledge.  Augmenting social perceptions of science with this truth will expand our awareness of how science works.  The necessary first step toward this goal is increasing awareness of this paradox and its implications within the scientific community.  This can be done by incorporating philosophy into the graduate-level training received by scientists or through continuing education.  In particular, the philosophy of science can help the scientist scrutinize whether the general conclusions about nature drawn from their studies are justifiable.  To be sure, the scientific community may be understandably reluctant to embrace those elements of philosophy that speak to science.  However, the stakes are too high to dismiss the paradox.  To leave the paradox unaddressed is to leave the assumption of nature’s uniformity unexplained, which necessarily undermines science-based decision-making.

By Jonathan M. Hanes, Ph.D.

Adjunct Assistant Professor at the Department of Geography of the University Wisconsin-Milwaukee, USA