According to the naturalism I call 'universal,' there is only one world: everything that exists is natural, which does not mean that everything that exists is material or physical, as today’s physics conceives matter. On the contrary, traditional naturalism or physicalism presupposes that everything is material, as matter is conceived by contemporary physicists. Since the 19th century, thanks to advances in the natural sciences, nature has tended to be defined as the reality studied by these sciences, and in particular by physics.

From a scientific and epistemological point of view, we can distinguish several natural strata: mathematical, physical, chemical, biological, psychological, and sociocultural. However, the continuity of nature, that is, real continuity, is the main thesis of universal naturalism, because without it, there would be several worlds, and for us, given the current state of our consciousness and knowledge, the supreme enigma of nature, of the real and unique world, is the incomprehension of this continuity. The existence of genuine enigmas, such as the one we are currently dealing with, highlights what is most extraordinary about human consciousness and our systems of symbols, a property that leaves us perplexed: the possibility to ask ourselves meaningful, rational questions that remain without rational answers.

The reader will probably say that the supreme enigma is not the continuity of natural strata but the meaning of our life, of our own individual and conscious human existence. There is, however, an even deeper question underlying that of the meaning of life: how is it possible to understand the continuity of the emergence of the conscious stratum endowed with a symbolic system, a language that allows us to develop propositions and ask questions such as that about the meaning of our interiority and subjectivity of our individual life?

A real enigma

‘Enigma’ has several synonyms whose meanings are similar but not identical. In this context, I conceive it as a reality that we are ultimately unable to comprehend. This is why it is more profound than a problem that can often be solved and whose solution may be implicit in its statement, as is often the case in mathematics. In this reflection, I also consider that an enigma is a reality that we necessarily seek to understand in a rational way, which is why it is not equivalent to the arcane or the mysterious, which are often accepted dogmatically and religiously. The enigma that concerns us here and now is the incomprehension of the continuous relationship between the different natural strata mentioned, a real union thanks to which, as I said, there is only one nature, one world.

In our case, the enigma is real because the continuous stages that lead from what exists only in potency in one stratum to what is actual in another are not intelligible (act and potency are Aristotelian concepts that we will discuss shortly). Here, I understand intelligibility in the traditional sense: it is the feeling we have when we understand something that takes into account our experience of entities and their qualitative properties. Neither modern thinkers nor our contemporaries conceive the feeling of intelligibility in exactly this way. For them, intelligibility tends to be idealistic, depending on our invention of concepts and mental categories and on the success of calculation and quantitative predictions. Aristotle leads us to imagine (at least I think so) that matter-potency is the deepest natural reality from which it is possible to try to understand the continuous unity of nature.

The idea of continuity according to some Aristotelian concepts

One of the first conditions that comes to mind when we say that two things are continuous is to think that there is a relationship between them. This is indeed a necessary but not sufficient condition for continuity. Two things can thus have a relationship between them without being continuous. The relationship between two continuous things implies their union, which in turn implies, as Aristotle established in his Physics, that their respective boundaries are not only in contact at the same place but that they merge.

According to this definition of continuity, any discrete entity, such as a mathematical point, that has no boundaries that merge with the boundaries of anything in its environment, is discontinuous. With this in mind, we can deduce that the continuous relationships between natural strata, responsible for the fact that there is only one reality, exist because these strata are made up of continuous entities, i.e., entities whose boundaries merge. But if two or more entities have boundaries that merge, that means there are not two or more entities, but only one.

If there is continuity between the physical-chemical-biological brain and consciousness, there are not, in reality, several entities, but only one. Epistemological multiplicity, insofar as there is no hyphen between the names of the sciences, if its plurality is definitive, reflects our lack of knowledge of real unity. The main objective of our epistemological multiplicity, far from being achieved at present, is to give an account of the fact that this multiplicity of aspects belongs to a single reality.

Potentiality, before being actualized, is unknowable

Using the Aristotelian concepts of actuality and potentiality, we can say today that consciousness experienced in act is potentially present in the biological stratum, and that what is actual in the biological stratum is potentially present in the chemical and physical strata. The continuous steps do not only go in one direction, from the physical-chemical to the biological, mental, and social. They also go in the opposite direction: the psychosocial and cultural have favorable or unfavorable consequences on the biological, chemical, and physical components of the organism.

An entity, for instance consciousness, before existing in actuality, exists in potentiality. Matter-potency is the capacity or potentiality that something has to produce a change in something else, and, more realistically and even more interestingly, the capacity to produce a change in itself. However, given that in order to know an object, it must exist in act, potentialities are not knowable before their actualization. A person is a potential musician if they know how to compose or perform a piece of music. This is a crucial, essential point: Matter-potency alone, before it is actualized, is incomprehensible and unknowable, and therefore, we cannot understand the continuity that exists between natural things before the results are in action. This is a major fact that contributes to the enigmatic nature of natural continuity.

The supreme enigma is, ultimately, the incomprehensibility of the continuity of matter-potency

The fundamental realities of nature, inspired by Aristotelianism, are matter-potency, space, motion, time, and causality. Matter-potency, as we have seen, is the ultimate substance present in everything that exists. For this reason, I believe, for my part, that the continuity of matter-potency is the ultimate foundation of the continuity of space, motion, time, and causality. On the other hand, according to Aristotle, the fundamental, essential continuum is that of space. The existence of what we now call space—Aristotle spoke instead of place—given its continuity, is the foundation of the continuity of movement. And since time presupposes movement, the continuity of movement establishes that of time. Finally, from all of the above emerges the continuity of causality.

Given that since modern times, in physics we no longer speak of matter-potency or prime matter, but rather of corpuscles, atoms, force, energy, and fields, and that quantum physics is now so important, one might think that the philosophical enigma of the continuity of nature no longer makes sense, but this is not the case. It should be noted, for example, that the description of fundamental particles by quantum mechanics tends to obscure a series of distinctions that are still considered crucial, such as the distinction between matter and its energy and between particles and forces. Quantum mechanics, at least for the moment, does not sufficiently clarify ideas. According to this science, it would seem that natural reality is ultimately both discontinuous and continuous.

In short, we have seen that in the context of universal naturalism, whose central thesis is the assertion that everything real is natural and that there is only one world, the supreme enigma is the incomprehension of the continuity of matter-potency, an incomprehension that makes it impossible to understand the real continuity between the epistemologically distinguishable strata.