Recent years have witnessed an increasing interest among philosophers of science in the topic of understanding. While earlier philosophers such as Hempel dismissed understanding as an uninteresting psychological by-product of explanations, nowadays many authors regard the notion of understanding as interesting in its own right. Kareem Khalifa is one of them, but his position is somewhat ambiguous, as he denies that understanding is distinctively valuable (p. 222). What Khalifa offers us is, in his own words, ‘a therapeutic fatalism in which understanding is worthy of [philosophical] attention even if it is not distinctively valuable’ (p. 229). His book is the culmination of a series of publications on the nature of scientific understanding and its relation to explanation. The title of one of the first of these is telling: Inaugurating understanding or repackaging explanation? (Khalifa ). This looks like a rhetorical question, implicitly accusing the ‘friends of understanding’ of selling old wine in new bottles. Indeed, Khalifa argues that understanding is basically nothing more than knowledge of an explanation: ‘give me an epistemology of explanation, and I will give you everything you could have wanted from a philosophy of understanding’ (p. 20). This has actually been the ‘received view’ (p. 18), which Khalifa traces back to his ‘intellectual heroes’, among whom he counts Carl Hempel and Wesley Salmon (p. 21). His book is meant as a defence and elaboration of that view, by means of a detailed and systematic analysis of the various debates and arguments about understanding in contemporary epistemology and philosophy of science.
After a brief survey of various kinds of understanding, Khalifa zooms in on explanatory understanding of empirical phenomena. In Chapter 1 he presents his ‘explanation–knowledge–science’ (EKS) model of explanatory understanding, according to which scientific understanding is basically nothing more than having ‘scientific knowledge of an explanation’ (p. 11). An important feature of the EKS-model is that it allows for degrees of understanding, since it presents a comparative account (p. 14):
(EKS1) S1 understands why p better than S2 if and only if:
(A) Ceteris paribus, S1 grasps p’s explanatory nexus more completely than S2, or
(B) Ceteris paribus, S1’s grasp of p’s explanatory nexus bears greater resemblance to scientific knowledge than S2’s.
Khalifa calls (A) the ‘nexus principle’ and (B) the ‘scientific knowledge principle’. The idea is that there is a spectrum of understanding, ranging from minimal understanding, via everyday understanding and typical scientist’s understanding, to ideal understanding (p. 15). Minimal understanding of why p is achieved when ‘S believes that q explains why p, and q explains why p is approximately true’ (p. 14). Khalifa adopts a difference-making account of explanation, and understanding simply is the grasping of an (approximately) true explanation. The prima facie elusive notion of ‘grasping’ is explicated as ‘nothing more than a cognitive state bearing some resemblance to scientific knowledge of some part of the explanatory nexus’ (p. 11).
Khalifa’s account of understanding is clearly reductive: understanding is reduced to knowledge of an explanation. But why does he add that this knowledge should be scientific? What does it mean to have scientific knowledge of an explanation? Wouldn’t it be more natural to claim that understanding is knowledge of an explanation, and scientific understanding is a subspecies in which one knows a scientific explanation? Khalifa doesn’t think so. He defines ‘scientific knowledge of an explanation’ as follows: ‘S has scientific knowledge that q explains why p iff the safety of S’s belief that q explains why p is because of her scientific explanatory evaluation’ (p. 12). Scientific explanatory evaluation (SEEing) consists in considering and comparing potential explanations and forming beliefs about them. Khalifa claims that scientists come to believe (or accept) explanations through SEEing, and that one’s understanding of why p is better the more one’s knowledge of the explanation of p is achieved in a way that resembles SEEing. Accordingly, on Khalifa´s account, merely knowing an explanation on the basis of testimony by a scientific expert does not qualify as scientific understanding, while this would qualify as such on the view that understanding is just knowledge of an explanation. This is an advantage that justifies the prima facie strange expression ‘scientific knowledge of an explanation’.
At this point, however, one may note that Khalifa’s conception of minimal understanding is quite weak: it is constituted by simply believing a true explanation, and requires no SEEing at all. By contrast, he holds a very demanding notion of knowledge, so that it is easy for him to devalue understanding. Moreover, it is far from obvious whether Khalifa’s deflationist conception of grasping is reasonable. He calls ‘grasping’ a mysterious ‘buzzword’, which apparently cannot have any meaning in itself and should therefore be used as a placeholder for cognitive states with more specific epistemic statuses, such as scientific knowledge (p. 14). However, this simply assumes, without any justification, that there is nothing philosophically interesting or meaningful about grasping. This assumption blocks a naturalistic approach to grasping, for example, via research in neuroscience or cognitive psychology. But there may be more to say about grasping, and then the EKS model might get into trouble.
In Chapter 2, Khalifa illustrates his account of understanding with a case study from the history of particle physics: the explanation of scattering phenomena. He argues that although Bjorken’s scaling laws provided an explanation of these phenomena, they failed to yield understanding for two reasons. First, the explanation was incomplete since the underlying microphysics was lacking (nexus principle). Second, Bjorken did not have scientific knowledge of the explanation as there was not sufficient experimental evidence for it (scientific knowledge principle). While understanding is a matter of degree, Bjorken’s explanation ‘did not hit the contextually relevant benchmarks’ (p. 35). The first problem was solved by Feynman, who provided the underlying microphysics with his mechanical parton model (later identified with quarks). The second problem was solved when scientists compared and evaluated Feynman’s model favourably with alternative explanations like Sakurai’s vector meson dominance model and Regge’s exchange model (SEEing). By adding a mechanical interpretation to Bjorken’s purely mathematical explanation, Feynman’s parton model clearly enhanced its intelligibility, allowing for qualitative reasoning using visual metaphors. Khalifa observes that the case thereby also fits de Regt’s contextual theory of scientific understanding (which he calls DRAU) and compares this analysis to his own account. However, his critique of DRAU is framed in general terms and scarcely refers to the Bjorken case. Where it does, Khalifa’s claim is that intelligibility (visualization, qualitative reasoning, and so on) is merely a means to the end of SEEing, which boils down to ‘good old fashioned hypothesis testing’ (p. 45). It seems to us, however, that this conclusion does scant justice to the desire for understanding expressed by physicists such as Paschos, who desperately exclaimed that ‘nobody seems to understand what this scaling means’ (quoted on p. 34).
In the remaining part of the book, Khalifa defends his account of understanding as a species of knowledge against alternative views that focus on differences between understanding and knowledge. The chapters address particular questions regarding differences between understanding and knowledge, which guide his analysis and structure the line of argument in the book:
Ability Question: Which abilities, if any, improve our understanding? (Chapter 3)
Objectual Question: Are comparably demanding cases of objectual and explanatory understanding identical in all philosophically important ways? (Chapter 4)
Explanation Question: Does understanding require explanation? (Chapter 5)
Truth Question: Does understanding require true belief? (Chapter 6)
Luck Question: Does understanding improve as it becomes less lucky? (Chapter 7)
Value Question: Do understanding and knowledge have the same kind of epistemic value? (Chapter 8)
The first question is addressed in Chapter 3: Does understanding require special abilities that are not required by knowledge? Khalifa’s approach to this issue is based on his idea that understanding comes in degrees: someone who believes an explanation that is approximately true has ‘minimal understanding’, and this requires no special abilities. To be sure, believing does require concept possession, and possessing the concept of ‘explanation’ requires the ability to answer what-if questions; but these abilities aren’t special, or so Khalifa argues (p. 59). However, the claim that believing an explanation is necessarily correlated with the ability to perform what-if reasoning appears too strong. A student may believe an explanation of the function of a specific electric circuit that her professor provides, even if she has no clue when asked what would happen if one of several LEDs is replaced with a resistor. It seems more plausible to us that what-if reasoning is a special ability that exceeds believing, or even knowing, an explanation. In the second part of the chapter, Khalifa discusses the views of Duncan Pritchard, Alison Hills, and Stephen Grimm, who defend in various ways the thesis that understanding involves ‘grasping’, a special ability that is not needed for mere scientific knowledge. He argues that any hypothesized ability is either excessive or redundant, and concludes that grasping isn’t special: it is nothing but having scientific knowledge of an explanation (p. 79).
In Chapter 4, the question of whether comparably demanding cases of objectual and explanatory understanding are identical in all philosophically important ways is discussed and answered affirmatively. Khalifa examines four ways of differentiation between objectual and explanatory understanding and argues that his EKS model of understanding can handle all these options. Objectual understanding only amounts to an abundance of explanatory understanding. The closely related question of whether understanding requires explanation is the object of Chapter 5. There, Khalifa presents and attacks Peter Lipton’s for the possibility of understanding without explanation. By applying his EKS model, Khalifa shows that the idea of understanding without explanation is untenable.
Chapter 6 addresses the question of whether understanding requires true belief. While knowledge is obviously ‘factive’—one can only know p if p is true—there is less agreement among philosophers about the relation between understanding and truth. In science, understanding is often achieved through idealized models, which contain (in the words of Catherine Elgin) ‘felicitous falsehoods’ that are crucial for their understanding-providing power. Understanding can even be produced with theories that are now considered as false, for example, with Newton’s theory of gravitation. Some authors (including Elgin and the authors of this review) see this as a reason to adopt a ‘non-factivist’ view of understanding, assuming that understanding why p does not require the explanans q to be true. Not surprisingly, however, Khalifa resists this: as his EKS-model aligns understanding with knowledge, he favours a ‘quasi-factivist’ approach, assuming that understanding why p on the basis of q requires that q explains why p is approximately true. Khalifa’s defence of quasi-factivism consists mainly in countering the arguments of non-factivists. Against the historical argument that earlier scientists did possess understanding even though we now know their theories are false (for example, that Priestley understood some aspects of combustion with phlogiston theory), Khalifa suggests that these scientists were at best ‘on the right track’ but did not have ‘full-blown scientific understanding’ (p. 166). However, he ignores that the pessimistic meta-induction implies that we may still have no scientific understanding whatsoever.
Chapter 7 deals with the question of whether lucky understanding is possible, a discussion that relates to the classic epistemological debates on Gettier cases, populated with sheep, bushes, fake barns, and partygoers dressed as firefighters. Although Khalifa regards understanding as a species of knowledge, which would appear to prohibit lucky understanding, he does tolerate a certain amount of luck in understanding. After discussing several possibilities of how the two might be related, Khalifa argues that analysis of scientific practice shows how understanding improves when explanations become safer (and thereby less lucky) due to scientific explanatory evaluation (SEEing, p. 195). He illustrates his claim with an account of how the understanding of peptic ulcers improved over the course of time.
The final chapter of the book discusses the value of understanding. While Khalifa acknowledges that understanding is valuable, he argues that it does not differ from knowledge in this respect: understanding and knowledge have the same kind of epistemic value. This claim will not surprise the reader of a book of which the core thesis is that understanding is a species of knowledge. Still, understanding might be a distinctively valuable species of knowledge. Alas, Khalifa denies this as well, arguing that understanding does not have any distinctive value over and above the value of knowledge. So why should philosophers even bother about understanding? As mentioned earlier, despite his negative conclusions regarding the alleged special nature and value of understanding, Khalifa still thinks that understanding is worthy of philosophical attention. But what does his ‘therapeutic fatalism’ (p. 225) amount to? Why would philosophers be interested in understanding if it can be fully reduced to explanatory knowledge? Khalifa’s short answer to this question is disappointing: ‘scientific improvements are increases of understanding, and scientific improvements are worthy of philosophical understanding’ (p. 229). In the final section of the book, Khalifa rightly observes that his fatalism echoes the view of his intellectual heroes, who regarded understanding as merely ‘an afterthought’ (p. 234). These heroes—Hempel, Salmon, and Kitcher—bypassed questions about understanding and focused their attention on scientific explanation. It is laudable that Khalifa has set himself the task of writing a whole book on understanding in their vein, but it is unclear why philosophers would continue their study of understanding if they accept Khalifa’s conclusions.
In sum, this is an important contribution to the debates about understanding in philosophy of science and epistemology. Indeed, one of the book’s unique selling points is that it crosses the divide between these two subfields of philosophy. Another is that it prevents friends of understanding from falling into a dogmatic slumber: it will stimulate them to sharpen their arguments if they believe that scientific understanding is distinctively valuable and distinct from scientific knowledge.
Henk W. de Regt
Anna E. Höhl
Khalifa, K. : ‘Inaugurating Understanding or Repackaging Explanation?’, Philosophy of Science, 79, pp. 15–37.