“Evolution is just a theory”, we sometimes hear, disapprovingly muttered.
“Climate change, it’s just a theory”, it is said, as if that was enough to stop the flood of evidence about our changing climate.
Calling something “just a theory” is often used as an easy way to belittle science. Referring to theories in this way makes it sound as though they are flimsy nonsense, easily rebutted and not to be taken seriously. Is that really the case?
Inevitably when discussing the meaning of words, it can be easy to descend into wordplay. The definition of a word changes over time and ultimately depends on the way it is used. At any point in time, one word may also have several different usages and the differences between them may be rather subtle.
In the scientific context in which we are interested, “theory” has quite a precise usage. “Theories”, the paleontologist Stephen Jay Gould wrote, “are structures of ideas that explain and interpret facts” (1). An established scientific theory will have been rigorously scrutinized and will form part of the body of knowledge. It will be a concept that is generally accepted and recognized.
That said, there is nothing immutable or invulnerable about a scientific theory. Einstein’s theory of gravitation has replaced Newton’s (although Newton’s is still good for most practical purposes). Indeed, even facts are not certainties either, but both make up elements of our knowledge of the world through science.
To say “it’s just a theory” about evolution, gravity or climate change is misinformed and lazy. To deride theories in this way is a much used and thoughtless denigration of science that often conceals an attack on a naturalistic outlook on the world, as if scientific knowledge is arbitrary and of little value.
This attitude is regularly accompanied by either a misleadingly innocent disregard or a surprising unawareness of the profound influence and power science has in our lives; from the practical, such as the technology we routinely use, or the medicine we take, to the astonishing and wondrous, in providing us with our understanding of the universe, from the most microscopic to the grand view of all that we can observe. Far from being “just a theory”, scientific theories are instead hard-fought-for knowledge, without which modern society would be impossible and our lives immeasurably poorer, both physically and mentally.
(1) Stephen Jay Gould, Evolution as Fact and Theory, 1981.