No one sets out to misunderstand a message, or to incorporate error knowingly into their thinking. We attend to signs because it matters that we do. A red traffic light is not something we interpret loosely. It brings movement to a halt, not because of anything intrinsic in the colour itself, but because we have learned—collectively and reliably—how to respond to it. If this were not the case, if meanings drifted from moment to moment, communication would become difficult to the point of collapse. For the most part, we hold these conventions in place without noticing them. They work quietly and with a certain discipline.
This quiet discipline can give the impression that meaning is somehow carried within the sign itself—as if the red light contains the instruction, or the word contains the thought that follows it. But we know, at least in practice, that this is not quite right. The same mark, gesture, or sound can serve different purposes in different contexts. What stabilises it is not its form, but the way it is taken up and used.
It is often said that symbols allow us to connect almost anything with anything else. That is broadly true, but it risks making the process seem more magical than it is. What makes such flexibility possible is not arbitrary invention alone, but a shared understanding of how a particular sign is to be taken. A word, a diagram, a line on a page—these do not operate in isolation. They depend on a background of agreement, training, and use. Without that, they remain marks among marks.
This is where talk of “rule-following” becomes helpful, though it can also mislead. We do not, in most cases, consult explicit rules before responding to a sign. Rather, we find ourselves already able to respond, having been brought into a practice where certain responses count as appropriate. A student learns what a line can do not by being given a definition, but by drawing, correcting, adjusting, and gradually recognising when something “holds” and when it does not. The rule is not separate from the practice; it is expressed through it.
Against this background, a familiar way of speaking within the biological sciences begins to look slightly strained. It is now routine to describe cells, neurons, and even molecules as “signalling.” The term appears so frequently that it passes almost without remark. Chemical gradients become messages; electrical activity becomes communication. The language is convenient, and perhaps even suggestive, but it carries with it an implication that is worth pausing over.
To speak of signalling is to borrow, however lightly, from a domain in which signs are used, interpreted, and responded to in ways that depend on shared practices. When we say that a traffic light signals “stop,” we are referring not just to a causal sequence, but to an established way of acting in response to a mark. The question, then, is not whether there are causal processes in cells or brains—there clearly are—but whether describing these processes as “signals” clarifies what is happening, or quietly shifts the description into a different register.
It is easy to see how the shift occurs. The language of signalling has a certain appeal. It seems to bring continuity across different levels of description, linking human communication with biological process. It also lends a sense of activity and direction to what might otherwise be described more plainly as chemical or electrical change. But this convenience may come at a cost. Where there are no shared practices, no negotiated uses, no possibility of getting it right or wrong in the relevant sense, it is not clear what distinguishes a “signal” from a cause.
This is not to suggest that scientists are careless, or that such language is used without awareness. Often it functions as a shorthand, a way of organising complex interactions into something more manageable. But shorthand has a way of settling into assumption. What begins as a metaphor can become, over time, a framework—a way of seeing that is no longer questioned.
The difficulty, then, is not simply terminological. It concerns what we take ourselves to be observing. If we say that a neuron sends a signal, we may feel that we have identified something akin to communication. But it may be that we have only redescribed a causal process in terms that belong elsewhere. The risk is subtle: not that we are wildly mistaken, but that we import distinctions that do not quite fit the case.
A more modest approach might be to keep these domains apart, at least initially. To describe cellular and neural activity in terms that reflect their causal organisation, without immediately reaching for analogies drawn from language or symbol use. This does not reduce their importance or complexity. If anything, it allows those features to be seen more clearly, without the overlay of familiar but potentially misleading categories. The question is not whether it is harmful to speak of biological signalling. It may be harmless in many contexts, and even useful. The question is what such language leads us to expect, and whether those expectations withstand closer examination. When we say that signs are present in a petri dish, what are we noticing, and what have we quietly assumed?
In practice, these distinctions often matter less than they appear to in abstract discussion. Work proceeds, experiments are conducted, results accumulate. But the terms we use still shape how those results are understood, and how further questions are framed. A small shift in language can redirect attention in ways that are not always immediately visible.
It may be enough, for now, to notice that the idea of signalling carries with it more than it first appears. It brings along a set of associations—about meaning, interpretation, and response—that belong most clearly to human practices.
Whether those associations illuminate or obscure what is happening at other levels is not something that can be settled in advance. It is something that has to be worked out, case by case, by looking closely at how the language is doing its work.
