The language of science is always so amazingly precise . . . except when it isn’t. Consider, for example, the word “life.”  Scientists have long struggled to determine exactly what qualifies as “life.” For instance, are viruses “alive?”

In the October 23, 2008 edition of Nature (available only to subscribers online), an article titled “Disputed Definitions” considers other often-used disputed terms.  The article is divided into sections written by specialists from the relevant disciplines. The subtitle of the article is “Nature goes in search of the terms that get scientists most worked up.”  Consider how often you encounter the following disputed terms.

Consider “paradigm shift,” made popular by Thomas Kuhn in his often-cited 1962 book, The Structure of Scientific Revolutions.  Kuhn argued against the then-popular view that science marched incrementally toward the truth. Sometimes, “normal science” doesn’t explain all of the phenomenon, straining a prevailing scientific theory.  If the strain of accommodating evidence is great enough “eventually some new science comes along and overturns the previous consensus. Voila, a ‘paradigm shift.’”  The often-used term “paradigm shift” is used in at least two ways, however. In its broad sense it encompasses the “entire constellation of beliefs, values, techniques and so on shared by the members of a given community.”  In the narrow sense, it refers to “concrete puzzle-solutions.”

Another often-debated (and currently fashionable) term is “epigenetic.”  Last year, Adrian Byrd suggested the following definition: “the structural adaptation of chromosomal regions so as to register, signal or perpetuate altered activity states.” Other scientists have savaged this definition, criticizing it because it “takes on-board pretty much every physical indicator of a gene’s activity.”  The battle over the term “epigenetic” is exacerbated by funding issues: the US National Institutes of Health recently began distributing $190 million as part of its epigenetics initiative, money which some non-recipients consider to be a big waste of money.  This outcry over the funding of epigenetic projects was the subject of a separate article in Nature (October 16, 2008, “Outcry at the scale of inheritance Project”).  In that separate article, “epigenetic” is defined as follows: “It is concerned with changes in gene expression that are typically inherited, but not caused by changes in gene sequence. In theory, epigenetic studies can help explain how the millions of cells in the human body can carry identical DNA but form completely different cell types, and perhaps why certain cells are susceptible to disease.”

Another commonly disputed term is “complexity.” M. Mitchell Waldrop (author of the 1992 classic, “Complexity: The Emerging Science at the Edge of Order and Chaos“) writes that complexity is not a unitary thing. James Crutchfield (head of the complexity sciences Center at the University of California, Davis) suggests that the remedy is to always add an adjective to the word “complexity” (such as “computational complexity” or “algorithmic complexity”).  What do all forms of complexity have in common? Consider Waldrop’s description:

Researchers have found plenty of undeniably complex systems to study, such as economies, ecosystems, urban traffic and brains. And in a qualitative sense, at least, these systems do have certain features in common that might serve as a definition. They are, for instance, all composed of many independent ‘agents’ (consumers, species, vehicles, neurons) that are constantly interacting with, and adapting to, one another. They all display a rich array of nonlinear feedback loop is among the agency, which means that small changes can have a big effect. And they never quite settled down into static equilibrium.

Here’s a word that kicks up my blood pressure: “race.” What is the problem with using the word “race”?

According to Erika Check Hayden, “It is controversial, it lacks a clear definition and the more that genetics reveals about race, the more biologically meaningless the term seems.”  Indisputable research now makes it clear that most diversity is beneath the surface:

A consensus now exists across the social and biological sciences: regardless of appearance or heritage, groups of human beings are overwhelmingly more genetically similar to each other than different. This doesn’t mean that race does not exist or is meaningless in society– far from it. But it does mean that an individual’s race is not a particularly useful or predictive indicator of biological traits or medical motor abilities. Race is “the social interpretation of how we look, and a race conscious society, says Camara Phyllis Jones [of the US Centers for Disease Control and Prevention]

Certainly, a person can see herself as belonging to a particular race to give context to social phenomena such as discrimination. “But in other contexts researchers are abandoning the term “race” in favor of other ways to group humans, by ‘population’, ‘genetic ancestry’ or ‘geographic ancestry.’”  For more good information on the controversy, check out the Wikipedia article on “race.”

The above terms are not an exhaustive list. Other “disputed terms” examined by this article include “tipping point,” “stem cell,” “consciousness,” and even “significant” (which one statistician called “diabolically tricky.”  Regarding consciousness, biologist Christof Koch is quoted as saying “What we need is a ‘theory of consciousness’.  Then we’ll be in a better position to define it.”

I’m not reporting on this Nature article to cast aspersions on the scientific enterprise.  My point is that scientists often try to study complicated subjects that compel an early exercise in ontology: carefully working to define exactly what it is that is being studied.