Abstract
Identifying the necessary and sufficient conditions for individuating and classifying diseases is a matter of great importance in the fields of law, ethics, epidemiology, and of course, medicine. In this paper, I first propose a means of achieving this goal, ensuring that no two distinct disease-types could correctly be ascribed to the same disease-token. I then posit a metaphysical ontology of diseases—that is, I give an account of what a disease is. This is essential to providing the most effective means of interfering with disease processes. Following existing work in the philosophy of medicine and epidemiology (primarily Christopher Boorse; Caroline Whitbeck; Alexander Broadbent), philosophy of biology (Joseph LaPorte; D.L. Hull), conditional analyses of causation (J.L. Mackie; David Lewis), and recent literature on dispositional essentialism (Stephen Mumford and Rani Anjum; Alexander Bird), I endorse a dispositional conception of disease. Following discussion of various conceptions of disease-identity, their relations to the clinical and pathological effects of the diseases in question, and how diseases are treated, I conclude (i) that diseases should be individuated by their causes, and (ii) that diseases are causal processes best seen as simultaneously acting sequences of mutually manifesting dispositions.
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Notes
To illustrate the distinction between conceptual and metaphysical analysis as I intend it, one can look to Hume’s work on causation. Hume began his conceptual enquiry by considering the collision of billiard balls, concluding that there are three aspects to the concept of causation: contiguity in space and time, constant conjunction, and necessary connection. Bearing his conceptual analysis in mind, Hume went on to provide one of the most influential metaphysical analyses in modern philosophy. He explained the nature of ‘necessary connection’ in causation, and what we were really referring to when we used the term in our conceptual and everyday causal talk. I do not pretend to do anything so revolutionary here, but the reasoning process in this paper is similarly structured -the conceptual precedes the metaphysical analysis of disease and its related concepts.
Note that according to this view the disease is not the invading pathogen itself—a virus in a petri dish is certainly not a disease. The ontological conception tells us that when a patient is suffering from a disease, the disease he is suffering from can be individuated purely by identifying the pathogen lodged in the patient. The pathogen causing disease d fixes the identity of d. The pathogen itself is not the disease.
See Fig. 1.
Insofar as LPAI strains do not have high mortality rates. There are reasons to keep track of LPAI strains as they can evolve into HPAIs.
Note that the ontological account is intended to be both a means of individuating diseases and an account of what a disease is
For now, consider a causal condition to be an event causally relevant to the contraction of the disease in question.
‘Mask’ is used here in Johnston's sense [6]—exercise might mask a patient’s disposition to get CVD just as dampening a match masks its disposition to light when struck.
This resultant picture forms an integral part of J.L. Mackie’s conception of singular causation [7], where Mackie identifies a cause as any ‘insufficient but non-redundant part of an unnecessary but sufficient condition’ (an inus condition), that is, any one condition to be found within what he terms, the ‘full-cause’.
From personal email correspondence with Alexander Broadbent, September 2013.
More on this in the next section.
My thanks to an anonymous referee for this observation.
I remain neutral as to whether the abnormal blood flow should be considered an essential part of the disease, or whether one should deem it merely an effect. Either way, even with ‘static’ conditions, medical practice and research tends to focus on how to prevent or stop the harmful resultant processes.
Note that this claim is equally true for naturalistic and constructivist interpretations of disease.
There are possible counterexamples, such as the decay of a radioactive particle, which seems to have no stimulus, but there is little need to get into this, here.
Perhaps with the exception of examples like randomly decaying radioactive particles, but these need not concern me here.
This gives rise to an interesting debate concerning the relationship between the dispositions of the person and the dispositions of her parts, but this is work for another paper.
From a purely theoretical, metaphysical perspective, to be convincing perhaps, one might need to talk about fundamental dispositional properties, and how the arrangement of their instances act as truthmakers for dispositional talk at a non-fundamental level. Reduction of the dispositions of people, organs, and cells to complexes of fundamental property-instances is not necessarily problematic, but more importantly, in the context of philosophy of medicine, these considerations are of little value.
Take the cause that makes ‘greatest causal contribution’ to be the cause that, individually, raises the probability of contracting the disease by the greatest amount.
‘Masking’ the properties initiating disease processes, or in other words, removing the causal base of a disease, is something we do on a very regular basis. Note that it also seems reasonable to suppose the absence of, say, a vaccination; that is, the non-introduction of a mask, can be a conceptually salient causal factor in contracting a disease. Again, this fits well with the Millian causal classification model provided above (as I have showed with the ‘scurvy’ case, the absence of some factor is often considered the most salient causal factor).
I shall leave it to philosophers of mind to argue over how!
This is perhaps an over-generalisation, but most constructivists would endorse such a claim.
My intuition is that the distinction is to be made in terms of the malfunction of bodily processes; this is generally entailed by the naturalistic accounts, but I take it that those opposed to this model need to provide a constructivist account of bodily malfunction.
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Acknowledgments
I would like to thank Alexander Broadbent, Kengo Miyazono, Michael Talibard, numerous members of The Munich Centre of Mathematical Philosophy, and two anonymous referees for their comments on earlier versions of this paper.
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Smart, B. On the classification of diseases. Theor Med Bioeth 35, 251–269 (2014). https://doi.org/10.1007/s11017-014-9301-9
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DOI: https://doi.org/10.1007/s11017-014-9301-9