In my work and my world, I am dealing routinely with whiplash-inducing headlines about health, and nutrition in particular (“no, wait, fruits and vegetables are bad for us this week!”) that raise questions about science, sense, and knowledge. When whatever we think we know, however reliably we think we know it, is called into question so routinely, it begs the question: how do we know?
My question is not how do we know any given thing, but rather - how do we know anything, ever, at all? The surprising answer is, we do not. Not unless we decide to trust our nervous systems and the perceptions they engender, for which there is a compelling case.
We do not, truly, know anything because all we can do is perceive. Were we in a virtual reality, like the one portrayed in the science fiction classic, The Matrix, we would likely be unable to know it, or prove it. We cannot disprove it now, either, since all of our perceptions of all of our disproofs would take place in the same virtual reality, reinforce it, and do nothing to tell us it wasn’t real.
We really can’t know anything for sure. But we can choose to have faith in the veracity of our impressions here, and build knowledge from them. If our perceptions are reliable, then what we derive from them is reliable, and so, too, are the embellishments of science, which are, essentially, extensions of our native perceptions via instruments and assays, lenses and equations.
It makes sense that our nervous systems and perceptions would be reliable since they are the ones we have here, wherever here is, and thus they are the ones adapted to be here. They are the perceptions that help us survive in this place where we are surviving.
We can, in effect, choose to have faith in our perceptions, and build our understanding from that foundation. The only alternative is to renounce the reliability of the only reality we know, and never understand anything. Most of us have made the choice long ago, if rather unconsciously.
What an intriguing, if ironic opportunity for bridge-building to concede that the origins of science reside in faith. Not faith in supernatural forces; faith in ourselves, faith in our perceptions, faith in our capacity to know- but faith, just the same. Knowledge and knowing do not begin with science, but with our faith in the reliability of constant or consistent patterns we perceive in the world around us. Knowing begins with our senses, and the common sense to trust them.
Science, then, extends those perceptions, dispels the denser shadows, reveals the hidden. But there is nothing an electron microscope or the Hubble telescope could show us that would remedy lack of trust in our native capacity to see. Science expands the realm of what we can know, only because knowing is possible in the first place, based on patterns we perceive in the world around us. The more constant the patterns, the more reliable- or even certain- our knowledge.
We know for certain that our reality is not THE reality, of course. We cannot, for instance, see infrared, or ultraviolet; but we know those wavelengths exist. To see the lesser rainbow bounded by our frail, human vision is to concede that what we “see” is not all there is to see, just our portion of it. The same limits pertain to our other senses. We do not hear ultrasound, but know it exists. We know that solid objects are made up of far more empty space than substance, yet- solid they seem to our fingertips, themselves more empty space than otherwise.
Science is not possible without faith in our perceptions, yet science itself tells us how limited those unaided perceptions are. Knowing within our sliver of reality, therefore, comes naturally; all the rest is rather harder.
How we know is of practical importance to us every day, for science is being abused. The science of climate change is abused by deniers of the long established and increasingly obvious, an indictment succinctly and elegantly made recently by one of our premier scientists, astrophysicist Neil deGrasse Tyson. The science of nutrition and health is abused every time a new round of headlines tell us everything we knew most reliably until yesterday, such as the general benefits of eating vegetables and fruits and legumes, is wrong again.
We did not suspect, we knew that apples fell down, not up from their trees before Newton. Had Newton’s calculations said otherwise, Newton’s formulas and not the apples would have been wrong. So, too, we know that a passing fixation on lectins does nothing to alter the established benefits of routine consumption of vegetables, fruits, and legumes; nor does a study overlooking the encompassing influence of social factors and environmental circumstance on health.
In this post-truth era, we seem to have forgotten, or at least allow ourselves to be mislead routinely about, what science is for.
Science is where knowledge extends, not where it begins. How interesting, with regard to diet, that every wild species on the planet knows what to feed itself, while owning no science at all. Our species presumably knew how to feed itself, too, until it started misapplying science to propagate doubt and perpetuate confusion.
Science is a method, a set of tools, and the most powerful we know, for answering hard questions that do not yield to casual observation and common experience. It is not for refuting what we know reliably and decisively on the basis of those humbler methods. Science cannot tell us that apples fall up out of trees, or that fire puts out water- for these are established as false where knowledge begins, in the realm of our native perceptions.
Science is for enhancing knowledge. It can find for us previously unknown things about lectins, and explore for us the idiosyncrasies of electrical fires. The reliability, verifiability, falsifiability, and replicablity of science are to be celebrated by all of us living in a modern world awash in its endowments.
But science simply isn’t for unknowing what was constant and clear before ever science was applied to it. We know that apples fall down from their trees and will continue to know that, no matter what new truths are teased out of gravity. We know, as well, that eating apples is good for us this week, as it was last.
The science of logic tells us something can be necessary but not sufficient, like any one enzyme in a biochemical pathway, or any one station in an assembly line. Common observation tells us something can be sufficient but not necessary, like any one route to a destination when others are at hand, or any one specific diet on a common theme fostering vitality and longevity.
Science, for all its independent marvels, depends on sense. Science is a powerful tool, and like any other power tool, can be used well or badly. For it to foster understanding rather than constant confusion in this age of alternative and competing “truths” on every important topic, we need to use it more sensibly.
This column follows a talk I was privileged to give recently to students in a Theory of Knowledge course at the Cheshire Academy taught by Mr. Chip Boyd. My thanks to Mr. Boyd, and his students, for the provocation!
David L. Katz, MD, MPH, FACPM, FACP, FACLM, is the Founding Director (1998) of Yale University’s Yale-Griffin Prevention Research Center, and current President of the American College of Lifestyle Medicine. He has published roughly 200 scientific articles and textbook chapters, and 15 books to date, including multiple editions of leading textbooks in both preventive medicine, and nutrition. He has made important contributions in the areas of lifestyle interventions for health promotion; nutrient profiling; behavior modification; holistic care; and evidence-based medicine. David earned his BA degree from Dartmouth College (1984); his MD from the Albert Einstein College of Medicine (1988); and his MPH from the Yale University School of Public Health (1993). He completed sequential residency training in Internal Medicine, and Preventive Medicine/Public Health. He is a two-time diplomate of the American Board of Internal Medicine, and a board-certified specialist in Preventive Medicine/Public Health. He has received two Honorary Doctorates.