Master your metaphors
Metaphors, like staining techniques in microscopy, create potentially useful artefacts for us to see – but like dyes they must be handled with care, writes Andrew Reynolds
12th December 2022
Aristotle claimed that “the greatest thing by far is to be a master of metaphor; it is the one thing that cannot be learnt from others; and it is also a sign of genius, since a good metaphor implies an intuitive perception of the similarity in the dissimilar.”[1] Metaphors are indeed more than just decorative literary devices – they are powerful tools of thought and reasoning. Philosopher IA Richards described them – metaphorically – as “speculative instruments”[2], and they can both help and hinder scientists’ efforts to understand reality and to shape it to our advantage. Biologists must ask themselves, as they do with any instrument employed in the conduct of their research, “will I be its master or its servant?”.
In the 17th century Robert Hooke described the microscopic spaces he observed in plant tissue as cells[3]. These weren’t really cells, but they didn’t have a name and reminded Hooke of the cells in bees’ honeycomb. Using the term ‘cell’ as a metaphor for these micro-anatomical structures provided 19th century researchers such as Schleiden and Schwann with a search image with which they developed the cell theory.
Productive comparisons
Cells were named for their similarity to bees’ honeycomb cells. The cell metaphor assisted in the observation and recognition of the universal occurrence of the cellular basis of life, but there was widespread debate over the term because not all ‘cells’ have rigid and easily discernible walls. Like how a stain applied to a slide can create misleading artefacts, the term highlighted an artefactual feature that was not universally true of biological reality. Similar remarks may be made of other historically important biological metaphors: the tree of life, the genetic code, transcription and translation, selfish genes and junk DNA, queen bees, slave-making ants, insect societies, invasive and keystone species, ecological niches and tipping points, and more recently the use of endonuclease ‘scissors’ such as CRISPR-Cas9.
A metaphor does more than simply supply a name or phrase by which to refer to something. Metaphor involves taking a word or phrase that is literally appropriate to one entity or process (what metaphor scholars call the source) and applying it to another entity or process to which it is not literally appropriate (the target). It is, therefore, a transgression of normal (i.e. literal) linguistic custom, but one that creates novel, and at times highly productive, comparisons between two things previously considered dissimilar.
Engines of advancement
In science, metaphors have proved to be very useful because they facilitate analogical reasoning, the process whereby scientists transfer what they understand about one subject or phenomenon to another seemingly disparate and less familiar one. This sometimes leads to the discovery or expansion of a more general pattern, phenomenon, mechanism or law. Metaphors and analogies might therefore be called the engines of scientific advancement.
Philosopher Mary Hesse noted that a scientific metaphor sets up three types of analogies between the source and target domains: positive, negative and neutral[4]. Features shared by both are positive analogies; features found in one alone are negative. All those we are as yet uncertain about are neutral analogies, and the effort to determine whether they count as positive or negative drives scientific research. Discerning deep and non-obvious positive analogies between dissimilar domains or phenomena counts as significant scientific discovery. Think of all the consequences that followed from the decision to describe DNA in terms of the ‘code’ metaphor: codons, transcription, translation, messengers and, more recently, editing, cutting and pasting of genetic sequences.
Similes also draw comparisons between two disparate things, but whereas similes emphasise mere similarity between two things (‘the ribosome is like a machine for manufacturing proteins’) metaphor suggests a deeper identity (‘the ribosome is a machine for manufacturing proteins’). This makes metaphor a more potent analogical device, but also potentially more misleading. It encourages us to take the implied identity almost without question. Machine metaphors, for example, encourage us to think of proteins (the target) not just as similar to machines in some superficial ways, but actually as a type of machine[5].
The danger is that a metaphor may cause us to focus so intently on the positive similarities between the source and target that we become blind to all the important ways in which they differ (the negative analogies). In that case, the metaphor may lead researchers astray or delay progress, and for that reason many people have expressed criticism of specific metaphors – including ‘selfish’ genes, plant ‘intelligence’, describing proteins, cells or organisms as ‘machines’ – as well as the use of metaphors generally[6,7,8,9,10].
Blurred lines
If a novel metaphor catches on, it may become a ‘dead’ metaphor. Think of a term such as chair leg. Everyone recognises that these are not animal legs – they really are legs, just of a different type.
The description of DNA sequences as a genetic 'code' has spawned further metaphors, such as translation, transcription, messengers, and more recently, editing - plus all manner of bad stock photos. This is known as polysemy, a kind of speciation of word meaning (another metaphor!). More scientifically significant examples of polysemy include: law of nature, causal mechanism, biological cell, natural selection, ecological niche and perhaps now we can add genome editing. Once novel – and typically contentious – metaphors, these have now become accepted, even literal, forms of speech. Or have they? The line between metaphorical and literal speech is fuzzier and more dynamic than we might suppose.
Examples like ‘the cell is a factory’ demonstrate that sometimes a metaphor can become literal not because it changes the way we use language, but because it changes the very nature of the thing being described metaphorically. The metaphorical description of the cell as a factory became literal when scientists genetically engineered bacteria to express the gene for human insulin (among others), turning these cells into literal factories for the production of valuable commodities. This was a hugely beneficial development for people with diabetes, but it illustrates another reason why metaphors must be used cautiously: they may end up changing not just the way we speak, but our environments, our societies and ourselves in very tangible ways. (Which version of the human genome will our descendants be running – H. sapiens 2.0?)
Because science and its products are not confined to the cell-like walls of laboratories or the pages of professional journals and magazines, scientists must also consider how their choice of language may be interpreted (or misinterpreted) in the larger societal context[11]. Metaphors that have become technical terms with well-defined and specific meaning for scientists can be misunderstood by non-scientists (e.g. selfish gene) and science communication frequently relies on the creation of novel metaphors to make helpful analogies for lay audiences.
Scientists, society and objective reality
Population geneticist Richard Lewontin consistently emphasised that science is a social enterprise conducted by human beings, who are themselves the products of society and whose research helps to remake (or preserve) that society and its economic and political structures and relations[12]. We can adapt Lewontin’s metaphor of the triple helix[13] – which he used to emphasise the interdependent relations among gene, organism and environment – to highlight the dialectical relationship between scientist, society and objective reality. The scientist attempts to depict reality (by proposing metaphors, concepts, hypotheses and theories), but is themself a product of a cultural and historical background that influences their language and metaphor choices – their science may in turn alter the reality they describe (both figuratively and literally) and impact the way future scientists speak and think about the world.
All three elements of this triple helix (scientist-society-reality) are therefore involved in an entangled co-evolutionary process. For instance, as Lewontin and many others have remarked, metaphorical language that gives genes and genetics causal primacy (DNA is the master molecule, genes are blueprints or programs) promotes a deterministic account of human biology and behaviour that often obstructs progressive social and health initiatives.
It is commonly assumed that the end product of science is an objectively true account of reality as it really is, independent of us humans. However, while science does involve the attempt to objectively describe the world (i.e. with as little bias as possible), we must remember it is created by humans and for humans to help us understand the world around us and to improve our chances of surviving and thriving in it. Consequently, good science has to be accessible to and useful for its target audience, a human audience that is continually evolving socially, technologically and politically over historical time. Metaphors help scientists make sense of the world and to communicate that understanding to students, politicians and other non-scientists.
Understanding for everyone
Like the dyes used to stain specimens of cells and tissues, our scientific language and theoretical accounts must latch on to real features of objective reality but do so in ways that assist our distinctly human abilities, limitations and objectives. As long as we do not mistake the colourful artefacts for the unvarnished truth or allow them to seep into places where they are less helpful, we can use scientific metaphor to refer to an independent reality, to help us make sense of it and to modify it in ways that optimally benefit us all, not just a powerful and privileged few.
Dedicated to the memory of Richard Lewontin (1929–2021), evolutionary biologist and sage critic of scientific metaphors.
Andrew S Reynolds is professor of philosophy at Cape Breton University in Nova Scotia, Canada. He is the author of The Third Lens: Metaphor and the Creation of Modern Cell Biology (University of Chicago Press, 2018) and Understanding Metaphors in the Life Sciences (Cambridge
University Press, 2022).
