1 Framing the Threshold: Halliday’s Taxonomy and the Question of Meaning
How far down does meaning go?
It is a question that has animated much contemporary work in biosemiotics, prompting scholars to trace the roots of semiosis into domains once thought devoid of communicative intent: cells, bacteria, plants, even molecular processes. Such work, while often illuminating, runs the risk of dissolving meaning into mere response, of flattening a concept born of consciousness into the structural regularities of matter or metabolism.
This series takes a different path. It begins not with a desire to find meaning in all things, but with the need to draw a careful boundary between value and meaning — and to do so in a way that preserves the rigour of a stratified model of complex systems.
The framework we adopt is that proposed by Michael Halliday in his theorisation of systemic functional linguistics. Halliday articulates a linear taxonomy of complex systems arranged along four primary strata:
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Physical systems – governed by physical forces and processes, devoid of life.
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Biological systems – living entities with metabolism, reproduction, and adaptation.
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Social systems – structured by interaction, organised through systems of value.
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Semiotic systems – constituted through symbolic value and meaning-making.
Each level builds upon the capacities of the former, but introduces a qualitatively new principle of organisation. Importantly, Halliday insists that not all value is symbolic. Social systems, including those of non-human animals and even non-conscious collectives, can be structured by systems of value that remain beneath the threshold of semiosis. Semiotic systems, by contrast, require symbolic abstraction — the capacity to construe experience through a system of signs, which presupposes consciousness.
In this light, the goal of the present series is to locate plant communication not in the semiotic stratum — where symbols operate — but in the social stratum, where interactions are patterned through relational value without symbolic mediation. In doing so, we retain fidelity both to Halliday’s taxonomy and to a broader relational ontology in which:
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Meaning is not a substance, but a construal of experience;
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Construal presupposes consciousness;
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And not all differentiation is meaningful — even when it is socially patterned.
Plants offer a particularly fruitful site for this enquiry. Through chemical signalling, root exudates, volatile organic compounds, and mycorrhizal networks, plants demonstrably participate in distributed, co-regulated interaction. They detect difference, respond to gradients, and modulate their unfolding in relation to others — but they do not construe experience. Their interactions are not symbolic, but they are not random either. They are structured by systems of value instantiated through fields of chemical relation.
This is not to diminish the complexity of plant life. On the contrary, to locate plants in the social stratum is to grant them a mode of organisation beyond the merely biological — a mode in which collective behaviour is patterned through shared fields of differentiation. But it is also to respect the threshold of meaning. For while plants instantiate value, they do not interpret it.
This distinction — between instantiating value and construing meaning — will serve as a guiding principle for the series. It aligns with the core tenet of the relational ontology underpinning this project: that meaning requires consciousness, but value does not; that systems can be socially organised without being symbolically constituted; and that the semiotic emerges not from mechanism, but from the threshold where experience becomes meaning through the act of construal.
In what follows, we will examine how plants participate in such value-structured organisation, without ever crossing into the symbolic. We will consider their detection systems, their distributed fields of interaction, and the rich social topologies they instantiate — all without recourse to metaphor, anthropomorphism, or mysticism.
We begin, then, at the edge of the sign — before the symbolic, but after the biological. At the point where life begins to organise itself socially, but not semiotically.
2 Rooted in Relation: Plants as Systems of Detection and Differentiation
In the preceding post, we located plants within the social stratum of Halliday’s taxonomy of complex systems. This positioning rests on a crucial distinction: while plants do not construe symbolic meaning, they nevertheless instantiate value-laden differentiation through patterned interaction with their environment and with one another. In this sense, they enact social organisation without consciousness.
To develop this further, we must understand how plants engage the world: not through awareness, but through systems of detection and differentiation that modulate their unfolding in response to structured fields of value. This post explores those systems — both in their biological detail and in their ontological significance.
Detection Without Construal
Plants do not sense in the way animals do. They possess no central nervous system, no sensory organs, and no capacity to model the world internally. Yet they detect and respond — often with remarkable subtlety — to gradients in light, gravity, touch, moisture, temperature, and above all, to chemical concentrations in soil and air. These responses are not reflexive reactions to fixed stimuli, but context-sensitive differentiations of process.
For instance:
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Phototropism adjusts growth towards light.
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Gravitropism orients roots and shoots with respect to gravitational pull.
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Thigmotropism modulates growth in response to mechanical touch.
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Chemotropism directs root growth based on chemical gradients, often shaped by neighbouring plants or microbial communities.
These are not symbolic actions, nor are they evidence of internal representations. They are differentiated unfoldings of the plant’s structure and behaviour in response to patterns in its relational environment. The plant neither "knows" nor "interprets" these conditions; it unfolds in relation to them.
In our relational ontology, this qualifies as the instantiation of value: the plant detects a difference that matters — a difference that modifies its unfolding. But it does not construe this difference as meaning. There is no interiority, no projection, no symbolic relation. There is value, but not meaning.
The Plant as Relational Topology
To say that a plant detects and differentiates is not to reduce its behaviour to stimulus-response. The environment to which a plant responds is not an object, but a relational field — a dynamic topology of gradients and interactions. Each unfolding of a leaf, root, or stem is conditioned by the co-unfolding of processes in the surrounding field: light filtered through neighbouring foliage; nutrients redistributed by microbial networks; chemicals secreted by kin or competitors.
The plant, in this sense, is not a bounded individual but a node in a relational topology — a process continually modulated by other processes. Its detection systems are not simply internal mechanisms, but distributed interfaces: surfaces of differentiation where chemical, photonic, and gravitational values are enacted.
To frame it differently: the plant’s body is an ongoing negotiation of values instantiated through interaction. It differentiates not in isolation, but in co-dependence with its environment. This relationality is neither abstract nor metaphorical — it is materially patterned and biologically regulated. It is also social in Halliday’s terms, insofar as it is shaped by interactional systems of value rather than individual metabolism alone.
From Differentiation to Organisation
The result is a form of organisation that is neither symbolic nor merely biological. It exceeds the logic of survival or reproduction and enters the domain of patterned sociality: spatial arrangements that maximise collective access to light; coordinated flowering among conspecifics; shifts in root distribution in response to the presence of neighbours. These are not actions taken by individuals for conscious purposes, but relational adaptations that instantiate systemic value.
This constitutes a crucial ontological threshold. For it is here — in the patterned differentiation of process in response to environmental gradients — that value begins to organise life beyond the level of the organism. Here, the plant is not just a living system, but a participant in a value-structured field — a field not yet semiotic, but no longer reducible to physiology alone.
No Symbol, No Self — Yet Still Social
To reiterate: there is no construal here, no sign, no interiority. The plant does not interpret light or nitrogen or kin. It unfolds in ways that instantiate patterned relations of value — relations shaped by the co-presence and differentiation of others. These unfoldings are social, but not symbolic; communicative, but not meaningful.
This distinction is subtle but vital. It guards against the temptation to project meaning where there is only modulation — to confuse value with signification. And it prepares the ground for what comes next: the investigation of plant interaction as a chemical conversation, structured not by symbols, but by distributed patterns of value enacted across a living field.
In the next post, we will explore that conversation — and ask how far a system of chemical signalling can go without crossing the threshold into semiosis.
3 Chemical Conversation: The Social Field of Plant Communication
Building on the understanding of plants as systems of detection and differentiation, we now turn to the dynamic chemical interactions that constitute their social organisation. Through an intricate web of signalling—root exudates, volatile organic compounds (VOCs), and mycorrhizal networks—plants engage in what can be described as a chemical conversation: a distributed, context-sensitive exchange of value that shapes collective behaviour.
Chemical Signalling as Social Interaction
Plants do not "speak" in a symbolic language, nor do they possess conscious intent. Yet they produce and detect a variety of chemical signals that modulate growth, development, and defence responses both within themselves and among neighbouring individuals. These chemical cues can:
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Indicate resource availability or scarcity, prompting adaptive root growth.
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Signal herbivore attack, triggering defensive chemical production in neighbouring plants.
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Coordinate flowering times or allelopathic interactions that influence spatial arrangement.
Such signalling forms a relational system in which the presence, concentration, and timing of compounds carry value—information that matters to survival and collective organisation, though not construed as meaning.
Distributed Agency and Co-Regulation
This chemical dialogue is distributed across a social field—a network of plants, microbes, fungi, and soil conditions—that dynamically co-regulate one another’s states. For example:
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Mycorrhizal networks function as communication channels allowing exchange of nutrients and signalling molecules.
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Volatile organic compounds (VOCs) released into the air can prime neighbouring plants’ defences.
Agency, here, is diffuse and relational, not centred in any individual organism. The system functions through mutual modulation, where each process affects and is affected by others in a continuous feedback loop.
Value Without Symbolic Mediation
The chemical conversation among plants exemplifies a system structured by value, not symbol. These signals are:
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Indexical or analogic, grounded in the physical-chemical properties of molecules.
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Context-dependent, where the same compound may have different effects depending on environmental or physiological conditions.
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Non-arbitrary, lacking the conventionality characteristic of human symbolic codes.
This reinforces the argument that plant sociality belongs to Halliday’s social stratum of complex systems: patterned by value, but not instantiated through symbolic meaning.
Implications for Biosemiotics
Recognising plant chemical signalling as value-structured but non-semiotic provides a disciplined framework for biosemiotic enquiry. It cautions against:
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Anthropomorphism, which risks projecting human-like intentionality onto plant processes.
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Over-extension of ‘meaning’, which dilutes the conceptual precision of semiosis.
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Simplistic binaries of sign/no sign, encouraging instead a nuanced cline from value to meaning.
This perspective opens fruitful avenues for exploring proto-sociality and distributed cognition without conflating these with consciousness or symbolic communication.
Towards a Non-Symbolic Sociality
In sum, plants participate in a sophisticated social field articulated through chemical differentiation. This field is a dynamic topology of value relations, enabling coordination and adaptation across individuals and species without requiring symbolic codes or conscious construal.
As we move forward into the next series, we will continue to delineate the boundaries and bridges between this chemical sociality and the emergence of semiosis proper, investigating the threshold at which value becomes meaning.
4 Value Without Meaning: A Biosemiotic Restraint
In previous posts, we established that plants engage in socially organised, value-structured interaction through sophisticated systems of detection and chemical signalling. Yet, crucially, these interactions do not cross the threshold into meaning as understood semiotically. This post examines why maintaining this boundary is essential, both conceptually and methodologically, within biosemiotics and the relational ontology framing this series.
Distinguishing Value from Meaning
At the heart of this enquiry lies a fundamental distinction:
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Value refers to relational differentiation that matters to a system’s unfolding. It structures interactions, guides adaptive behaviour, and sustains social organisation.
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Meaning, by contrast, is a construal—an interpretive act enacted by a conscious agent who recognises signs as symbols and assigns significance beyond immediate context.
Plants instantiate value but do not construe meaning. Their chemical signals carry indexical or analogic information, grounded in physical relations, but they lack the symbolic abstraction that characterises semiotic systems.
The Importance of Ontological Discipline
Why is this boundary important? Two principal reasons arise:
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Conceptual Clarity:Collapsing value into meaning risks diluting the analytical power of biosemiotics. If everything that differentiates becomes meaningful, the concept loses specificity and explanatory force.
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Avoidance of Anthropomorphism:Projecting symbolic interpretation onto plants obscures the unique modalities of human semiosis and consciousness. It underestimates the radically different forms of organisation at play in non-conscious social systems.
By respecting this boundary, we preserve a stratified ontology of complex systems, honouring the qualitative leaps from physical to biological, social, and semiotic organisation.
Value as a Necessary but Not Sufficient Condition for Meaning
Value can be understood as a precondition for meaning. Without differentiation that matters, symbolic interpretation cannot arise. Yet the presence of value alone does not guarantee semiotic construal.
In the relational ontology at the core of this series:
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Value structures the field of potentiality in which systems unfold.
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Meaning emerges only when conscious construal actualises select relations within that field.
Thus, plant sociality reveals a proto-social realm—rich in pattern and coordination, but silent with respect to symbolic semiosis.
Methodological Implications
For researchers and theorists, this restraint calls for:
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Careful terminological precision, differentiating between value-driven modulation and meaning-making.
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Analytical frameworks that can model distributed agency and relational fields without defaulting to semiotic assumptions.
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Openness to alternative logics of organisation, such as analogic, indexical, or morphogenetic codes, which operate below the semiotic threshold.
Conclusion
Maintaining the distinction between value and meaning is not an exercise in gatekeeping, but an act of ontological and epistemological fidelity. It allows us to recognise and honour the social complexity of plants without conflating their modes of interaction with human semiotics.
In doing so, we deepen our understanding of how life organises itself across multiple strata of complexity — from the physical through the biological and social, up to the semiotic.
In the next series, we will explore how these principles apply to animal social systems, where consciousness and symbolic semiosis begin to emerge.
Reflective Coda
In this series, we asked what it might mean to take the life of plants seriously — not only biologically, but socially and semiotically. We approached this question without presuming that plants think, speak, or mean in any human sense. Instead, we began with a simpler, more radical proposition: that detection, differentiation, and response are already the roots of value — and that value, not symbol, is the first ground of meaning.
Plants as Socially Organised Systems
We saw that plants:
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Detect gradients, differences, and chemical signatures in their environment,
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Coordinate with other plants through chemical signalling,
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Adapt their growth, development, and reproduction in response to their ecological context.
Though devoid of nervous systems or consciousness, these capacities are structured, collective, and consequential. They reveal an organised responsiveness to value — a proto-social dynamic that operates beneath the level of meaning-as-symbol but above the level of mechanistic reaction.
Value Without Meaning, Organisation Without Mind
We proposed that such systems operate before the sign — in a space where value is enacted but not construed, differentiated but not symbolised. In this way, plants teach us something profound:
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That not all social organisation requires consciousness,
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That meaning may emerge from systems which do not themselves “mean.”
This opens the door to a non-anthropocentric model of value: one grounded in interaction, organisation, and potential — not in mind or message.
A Semiotics of the Living
By reframing plant processes as socially organised differentiation, we position them not at the periphery of meaning, but at its threshold. The chemical emissions of a damaged leaf are not signs in the linguistic sense — but neither are they noise. They instantiate patterned value, shaping the future of their receivers.
In this, they model the prerequisites for meaning: pattern, relevance, co-orientation, and difference. And they invite us to think not just of what meaning is, but how it becomes.
Conclusion: At the Threshold
This series brings us to a threshold — not of human language, but of life as semiotic potential. Plants show us how meaning begins: not with representation, but with relation; not with symbol, but with value.
In the next series, we will follow this thread through animal sensing, proto-semiosis, and the rise of symbolic systems — asking how the construal of value gives rise to the human worlds of sign, structure, and significance.
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