Evolution Through the Lens of Potency in Metaphysics

Every star, every cell, every living creature you see today was once a possibility waiting to unfold. The universe did not arrive in its current form all at once. It emerged – layer by layer, stage by stage – from a state of raw potential into the richly structured reality we inhabit. This is precisely the kind of transformation that the metaphysical concept of potency was designed to explain. When we look at evolution – both cosmic and biological – through the lens of potency, the entire history of the universe begins to look like one grand movement from what could be to what is.

What is potency in metaphysics? 🔗

In the Aristotelian-Thomistic tradition, all of reality can be understood through two complementary principles: act and potency. Act refers to what a thing currently is – its present reality, its determinations, its actual properties. Potency, on the other hand, refers to what a thing can become – its capacity for change, development, or new determination.

Consider a block of marble. Right now, it is just a block. But within it lies the capacity to become a statue of Apollo. That capacity is its potency. Once a sculptor carves it into the statue, the potency has been actualized – it has moved from potency to act. This is the classic example that both Aristotle and Thomas Aquinas use repeatedly.

As the Catholic Encyclopedia explains, potency is not just a statement about the future; it implies a genuine, real aptitude within a thing to receive new forms or determinations. Potency is something more than mere logical possibility. It exists in real subjects that are capable of change. Meanwhile, act is not limited to physical action – it encompasses any perfection, determination, or fulfillment that a thing possesses.

This distinction is critical. Without it, change itself becomes unintelligible. If something is already fully actual, it has no room to become anything new. If something is pure nothingness, it has no capacity to become anything at all. Potency is the middle ground – a real but not-yet-actualized capacity – that makes change, growth, and evolution metaphysically possible.

The Big Bang: cosmic potency in action 🔗

Modern cosmology tells us that the universe began roughly 13.8 billion years ago from an extraordinarily dense and hot initial state. In the language of metaphysics, this initial state was loaded with potency – an almost unimaginable concentration of capacity for becoming.

At the moment of the Big Bang, there were no stars, no galaxies, no planets, no molecules, and no living organisms. None of these things existed in actuality. Yet the conditions for all of them were latent within that primordial state. The philosopher Colin McGinn captures this vividly when he describes the initial state of the universe as something akin to a seed – tiny, homogeneous, and undifferentiated, yet containing within itself the potential for the vast plurality of objects that would eventually populate the cosmos.

From a metaphysical standpoint, the history of the cosmos is a progressive actualization of potencies. First, elementary particles formed as the initial energy cooled. Then atoms emerged. Gravity drew matter into clouds, which collapsed into stars. Stars forged heavier elements in their cores and scattered them through supernovae. These heavier elements combined into molecules, and eventually into planets. Each stage is a transition from potency to act, with each new actuality carrying within it further potencies for the next stage of development.

Why a pure potency cannot actualize itself 🔗

One of the key metaphysical principles at work here is that potency cannot actualize itself. A block of marble does not carve itself into a statue. Something already in act must serve as the cause that brings a potency to fulfillment. This principle has profound implications for cosmology. If the initial state of the universe was pure potency – raw, undetermined capacity – then something already actual must have been responsible for setting the process in motion. This is the reasoning behind classical cosmological arguments for a first cause or an unmoved mover, an entity of pure act that initiates the chain of actualization without itself requiring further actualization.

Whether one accepts the theological conclusions of this argument or not, the metaphysical structure is worth understanding. The Big Bang, viewed through the lens of act and potency, is not just a physical event. It is the first great instance of potency being moved to act – the beginning of a process that has been unfolding ever since.

Biological evolution: potency at the cellular level 🔗

The same metaphysical framework applies when we shift from cosmology to biology. The evolution of life on Earth is another expression of potency progressively actualizing into increasingly complex forms.

Life on Earth began with simple, single-celled organisms roughly 3.5 to 4 billion years ago. These early cells were prokaryotes – organisms without a defined nucleus. They were simple in structure, but they carried within themselves an enormous range of developmental potential. Over billions of years, this potential was gradually actualized through processes of mutation, natural selection, and environmental interaction.

From single cells to complex organisms 🔗

The emergence of eukaryotic cells – cells with a nucleus and complex internal structures – marks one of the most significant transitions in evolutionary history. Eukaryotes had a different developmental potential from prokaryotes, one that became apparent particularly as oxygen levels in the atmosphere rose. This new cellular architecture carried within it the potency for multicellularity, tissue differentiation, and eventually the vast diversity of animal and plant life.

The Stanford Encyclopedia of Philosophy highlights how the concept of potentiality plays a central role in developmental biology, particularly in understanding stem cells. A fertilized egg, or zygote, possesses the potency to develop into a complete adult organism – a potency that is progressively narrowed and specified as the cell divides and differentiates. Early embryonic stem cells are pluripotent, meaning they can become nearly any cell type in the body. As development proceeds, this broad potency narrows: a blood stem cell can become many types of blood cells but cannot become a neuron. Each step of differentiation is a movement from broader potency to more specific act.

This mirrors the Aristotelian principle precisely. The potency of the zygote is real – not merely hypothetical – but it requires the right conditions, the right environment, and the right triggers to be actualized. The process of embryonic development, from fertilized egg through cleavage, gastrulation, and organogenesis, is a carefully orchestrated sequence of potencies being brought into act.

The Roux-Driesch debate: a potency puzzle 🔗

The question of how potency operates in developing organisms was at the heart of a famous late-19th-century debate between two embryologists. Wilhelm Roux argued that during cell division, inherited elements become unequally distributed among daughter cells, leading to distinct cell fates. Hans Driesch, on the other hand, held that each cell retains its full potential even after division. This debate, as detailed in the developmental biology literature, touches directly on the metaphysics of potency: is the potency of the original cell divided and distributed, or does each new cell retain the full range of possibilities?

Modern biology has shown that the answer is nuanced. While cells do progressively restrict their developmental potential through differentiation, certain cells (such as stem cells) retain broad potency, and under specific conditions, even differentiated cells can be reprogrammed back to a pluripotent state. This suggests that potency in biological systems is not simply lost during actualization – it can, under certain circumstances, be recovered or redirected.

Bridging metaphysics and science 🔗

One of the most valuable aspects of the potency-act framework is its ability to bridge metaphysical theory and empirical scientific findings. Metaphysics asks why change is possible at all. Science asks how specific changes occur. The two are not in competition – they operate at different explanatory levels.

The process metaphysics approach, advocated by thinkers like John Dupré, suggests that organisms and even species are best understood not as static things but as ongoing processes. From this perspective, evolution is not something that happens to fixed substances; it is the very nature of biological reality. Organisms are processes of continuous actualization, and the evolutionary history of life is a vast, interconnected web of potencies being brought into act across billions of years.

Meanwhile, the process view of biological organisation challenges the traditional Aristotelian notion that development is the unfolding of a pre-existing potential encoded in the organism’s form. Instead, contemporary developmental biology shows that development is a genuinely creative process – one in which the organism and its environment interact to produce outcomes that were not simply pre-programmed. Potency, in this view, is not a fixed blueprint but an open-ended capacity shaped by context.

Evolution as the continuous unfolding of potentiality 🔗

When we step back and view the entire history of the universe – from the Big Bang to the emergence of consciousness – we see a single, continuous narrative of potency being actualized into ever more complex and differentiated forms.

The initial state of the universe held the potency for particles. Particles held the potency for atoms. Atoms held the potency for molecules. Molecules held the potency for cells. Cells held the potency for organisms. And organisms held the potency for beings capable of reflecting on the very process that produced them.

Each stage did not create something out of nothing. Rather, each stage actualized a capacity that was already latent in the preceding stage. This is what makes the concept of potency so philosophically powerful: it provides a coherent account of how genuine novelty can emerge without violating the principle that something cannot come from nothing. The new thing was already present – not as an actual reality, but as a real capacity waiting for the right conditions.

This perspective also raises important questions about the future. If the universe has been a story of potency being actualized, what potencies remain? What further forms of complexity, organisation, or consciousness might emerge from the capacities latent in the current state of the universe? The metaphysical principle of potency suggests that the story of the universe is not yet finished – that reality still contains unrealised capacities waiting for the right conditions to unfold.

The limits of potency 🔗

It is worth noting that potency is not unlimited. A rubber ball has the potency to become flat or rough, but not to become sentient or capable of arithmetic. Potency is always constrained by the nature of the thing that bears it. This applies at every level: the potencies latent in the initial state of the universe were determined by its physical properties, and the potencies of a given cell are determined by its genetic makeup and cellular environment.

This principle – that act is limited by potency – is a cornerstone of Thomistic metaphysics. The specific form of Apollo actualizes and is simultaneously limited by the portion of marble it inhabits. Likewise, the evolutionary potential of a species is constrained by its genetic architecture, its ecological niche, and the physical laws governing its environment. Evolution is not an unconstrained exploration of all possible forms; it is a structured process in which specific potencies are actualized within specific limits.

What do you think? If the entire history of the universe can be understood as a progressive movement from potency to act, does this suggest that there is a direction or purpose embedded in the structure of reality? And if potency requires something already actual to bring it to fulfillment, what does this imply about the ultimate origin of the process?

References

1. https://en.wikipedia.org/wiki/Potentiality_and_actuality
2. https://www.newadvent.org/cathen/01124a.htm
3. https://en.wikipedia.org/wiki/Big_Bang
4. https://www.colinmcginn.net/big-bang-metaphysics/
5. https://www.ncbi.nlm.nih.gov/books/NBK6472/
6. https://plato.stanford.edu/entries/biology-developmental/
7. https://royalsocietypublishing.org/doi/10.1098/rsfs.2016.0148
8. https://karger.com/hde/article/67/5-6/233/869596/The-Metaphysics-of-Development-and-Evolution-From