Abstract

Keywords

۱٫ Introduction

۲٫ What is life?

۳٫ What is a virus?

۴٫ Do any virus-like systems achieve closure to efficient causation?

۵٫ Conclusion

Declaration of Competing Interest

Acknowledgements

Appendix A. Supplementary data

References

Abstract

Whether or not viruses are alive remains unsettled. Discoveries of giant viruses with translational genes and large genomes have kept the debate active. Here, a fresh approach is introduced, based on the organisational definition of life from within systems biology. It views living as a circular process of self-organisation and self-construction which is ‘closed to efficient causation’. How information combines with force to fabricate and organise environmentally obtained materials, given an energy source, is here explained as a physical embodiment of informational constraint. Comparing a general virus replication cycle with Rosen’s -system shows it to be linear, rather than closed. Some viruses contribute considerable organisational information, but so far none is known to supply all required, nor the material nor energy necessary to complete their replication cycle. As a result, no known virus replication cycle is closed to efficient causation: unlike cellular obligate parasites, viruses do not match the causal structure of an -system. Analysis based in identifying a Markov blanket in causal structure proved inconclusive, but using Integrated Information Theory on a Boolean representation, it was possible to show that the causal structure of a virocell is not different from that of the host cell.

Introduction

The first half of 2020 has seen one particular virus (SARS-Cov2) dominate world news, so much that viruses appear to be at the forefront of public interest in biological research and in this context an old debate has reemerged: “Are viruses alive?”. According to an informal survey (Racaniello, 2014), expert opinion remains divided roughly a third each between yes, no and don’t know. This is not surprising given that the debate seems still to be resolved. Eleven years ago, an emphatic statement was made against including viruses among the living (Moreira and Lopez-Garcia, 2009), quickly countered by (sometimes indignant) responses of matching boldness (Claverie and Ogata (2009); Hegde et al. (2009)) and more nuanced responses (e.g. Forterre (2010b)). The discovery of giant viruses(Raoult and Forterre, 2008; Abergel et al., 2015; Claverie and Abergel, 2018), especially the Pandoraviruses, having genome sizes reaching that of parasitic eukaryotes (Nad`ege et al., 2013) and Tupanviruses with their batteries of translational genes (Abrah˜ao and et al., 2018; Rodrigues et al., 2020) has further stirred the debate (e.g. Claverie and Abergel (2010); Abergel et al. (2015); Brandes and Linial (2019)). It also attracted philosophers of science who having analysed the debate, concluded that it is misguided (van Regenmortel, 2016; Koonin and Starokadomskyy, 2016). Whether or not viruses belong within the category of living has again become highly topical and contentious.