The Holism Reductionism Debate in Ecology

The philosophical debates that have accompanied the development of science have often been expressed in terms of dichotomous choices between opposing viewpoints about the structure of nature, the explanation of natural processes and the appropriate methods for research.

We can ask if the different levels of organization⁵ such as the atomic, the molecular, the cellular, the organismal, the species, and community level are only the epiphenomena of underlying physical processes or whether the levels are ontologically separated by real discontinuities. Or, put differently, if the objects at one level are fundamentally similar despite apparent differences, or whether there is only one basic ontological level despite the seeming similarities between objects at different levels.

The holism-reductionism controversy in ecology is about the relationship between wholes and their parts (Lewontin et al, 1980; Bergandi, 2011; Trepl et al, 2011). The contrast between reductionism and holism in ecology tends to take the form of an opposition between individualism and

5 I shall refer to the different levels of organization in ecology henceforth respectively as: population as a collection of individual organisms of the same species; community as a collection of species’ populations; ecosystem as a collection of communities and their physical environment, thus, as a unit of biological organization made up of all of the organisms in a given area interacting with the physical environment.

7 organicism. Community, according to individualism, is merely a name for a certain collection of individual organisms, gathered together more or less at random, who are considered to be autonomous and who alone are seen to be real. In organicism, by contrast, community is conceived as an organic entity or as a superorganism. In other words, the relationship between the part and the whole is conceptualized in analogy to the relationship between cell/tissue/organ and organism. The idea entailed by organicism is that a biotic community is of the same character as an individual organism.

It might be argued that what links together all the variants of the holistic thesis is not much more than the principle that “the whole has priority over the parts”- whatever “priority” might mean exactly – and a set of reservations about any form of reductionism. On the reductionist side, what is common between different variants of this thesis is arguably above all the commitment to derive statements about phenomena of a complex nature from statements about phenomena of a simpler nature, and that science essentially consists in this kind of reduction.

To encompass the whole classical holism-reductionism debate in ecology it is useful to map out a clear conceptual, logical and epistemological framework (Bergandi, 2011).⁶ By revealing the basic assumptions of each theoretical approach, we should be better able to understand the points that are similar and shared, as well as the incommensurable ones. It is however important to note that in ecology, as in all other natural sciences, the ontological and epistemological foundations are essentially naturalistic and materialistic. Thus, it is thought that we can understand all objects, processes and events without references to vitalistic, supernatural, teleological or theological entities and causes. The order and laws structuring reality are in principle intelligible, and the way to seek knowledge is through a scientific and naturalistic epistemology. This naturalistic standpoint should be remembered every time we use the key terms of “holism” and “reductionism”.

In ecology, the classical confrontation between holism and reductionism plays a structuring role, and we must be aware that their basic assumptions involve different and generally antinomian ontologies (worldviews), methodologies (research strategies) and epistemologies (Trepl et al., 2011).

The theories and methods that are called holistic differ greatly according to which aspect of the concept of wholeness they highlight (Trepl et al., 2011). It is the organic interaction of the parts that constitutes the holistic element in life. According to this view, for biological holism the key element of life is not seen to lie in an inner force inaccessible to scientific methods. Biological holism consists, instead, in the view that the characteristic of being alive can only be attributed to objects that are a whole, and that this whole exists in a special relationship to its parts that is not found in non-living objects. Understanding these wholes requires an epistemic approach that is different from that of physics. To the extent that holistic theories divide reality into different levels or autonomous wholes they can be called ontologically pluralistic.

Conversely, the reductionist ontology has its antecedents in the mechanistic worldview, originating with the Greek Atomists, in which reality has been defined from an atomistic perspective:

reality consists of distinct, discrete, invisible atoms with fixed spatial-temporal amplitude. Unlike reductionism, the ontological perspective of holism is continuistic and relational: reality consists of a continuum of events and processes that are intrinsically interconnected and interdependent.

6Bergandi (2011, pp 31-32) argues that the issue is easier to grasp if we keep in mind that holism generally represents the ontological background of emergentism but does necessarily coincide with it. Thus we can speak, in very loose terms, of the holism-reductionism debate, although it would be better characterized in terms of emergentism and reductionism. However, in definitional terms, there is not just one kind of emergentism and reductionism, but various kinds of it. There is a point of contact between holism and emergentism, but holism demands something more: the character of wholeness as an active cause.

8 At first sight, both reductionism and holism share a common scientific philosophy, namely, that all biological phenomena are fundamentally physico-chemical and that the laws of physics and chemistry are applicable to biological phenomena. Nevertheless, holism holds that the various levels of organization are characterized by new and specific properties (Lovejoy, 1927; Philips, 1935;

Ablowitz, 1939; Emmeche et al., 1997; Kim, 1999; Humphreys, 2006; MacLaurin and Sterelny, 2008;

Bergandi, 2011; Santos, 2015; O´Connor, 2020; Santos, 2020). These emergent properties increase the degree of complexity of a given level compared with the various levels of which it is composed.⁷ For this reason, even if physics and chemistry are normally applicable to ecological phenomena, each level of organization acquires appropriate laws and can be explained by theories that allow for an understanding of the specific properties of that particular level. By contrast, reductionism denies the existence of emergent properties or else considers them an epiphenomenon strictly dependent on the state of our knowledge, in the sense that these properties will eventually be explained, by the identification of the components and mechanisms from which they supposedly emerge.

These ontological assumptions have significant consequences in the methodological and epistemological domains (Bergandi, 2011): reductionism considers that at a given level of organization, the analytical study of constituent parts and their relations is necessary and sufficient to predict, or at least explain, all the properties of that level. Fundamentally, reductionism is a “bottom-up” strategy (Bergandi, 2011), which takes into account the level at which the events to be explained occur, e.g., the ecological level, as well as the lower levels that contribute to the explanation, e.g., the chemical and physical, for example. An analytical and additive method, therefore, dissects the entity, or decomposes the process into its component parts and attempts to take into consideration the relations among them. A successive summation of the individual component intrinsic properties or interactional properties should allow the extrapolation of the global properties of the entity as a whole.

Methodologically, the holistic approach, while recognizing the need for analytic decomposition, considers its explanatory power limited. In fact, from the holistic perspective, the feedback interactions that link different levels of organization play a role of the utmost importance in the determination and causation of emergent properties. This approach does not limit the analysis to the constitutive parts of –or their relations in – a specific level of organization. For this approach, both the higher levels (“downward causation”) and the lower ones (“upward causation”) participate in determining the properties of specific levels. It is a multilevel triadic approach, which constitutes a methodological necessity in holism.⁸

After this brief introduction to the Holism-Reductionism debate in ecology, I will now describe and scrutinize, in more detail, the classical positions on these controversies, and their more recent developments, which have shaped the development of ecology in the 20^th century. My objective

7 According to Kim (1999, pp. 3-4), at the core of the ideas associated with emergentism is the thought that as systems acquire increasingly higher degrees of organizational complexity they begin to exhibit novel properties that in some sense transcend the properties of their constituent parts, thus behaving in ways that cannot be predicted on the basis of the laws governing simpler systems.

8 According to Kim (1999, pp. 22-23), when we analyze an ecological situation from the perspective of the layered model, with differentiated levels, we see that the following three types of inter- or intra-level causation must be recognized: (i) same-level causation, (ii) downward causation, and (iii) upward causation. Same-level causation, as the expression suggests, involves causal relations between two properties at the same level – including cases in which the instantiation of one property causes another property to be instantiated. Downward causation occurs when a higher-level property, which may be emergent, causes the instantiation of a lower-level property; similarly, upward causation involves the causation of a higher-level property by a lower-higher-level one. Kim believes that, for the emergentist, there is good reason to believe that downward causation is fundamental and of crucial importance. For it can be shown that both upward and same-level causation (except same-level causation at the ultimate bottom level, if there is such a level and if there are causal relations at this level) presupposes the possibility of downward causation. I agree with this position, which I will develop below in the section on holistic systems approach.

9 will be, at the end of the analysis, to characterize a moderate approach, with elements from both positions, which should become important to explain ecological phenomena, within my perspective.