Sistema hueso-implante-prótesis

According to the Peircean view, IBE is primarily an argument for pursuing a hypothesis rather than an argument for accepting it. More generally, having a high degree of explanatoriness provides some reason for pursuing a hypothesis. In this section, I will first present an account of how explanatory reasoning justifies pursuit before showing how this allows the Peircean view to avoid the problems outlined in the preceding section. In a nutshell, my account of why explanatoriness provides reasons for pursuing a hypothesis H is that this makes it epistemically valuable to learn that H is true. First, consider how this account works in an IBE. We start from the premise that H would provide the most satisfying explanations (or would provide the most understanding) out of a set of rival explanations, if it were true. Thus, if we were to learn that H is in fact

true, this would be an epistemically valuable outcome, and indeed the optimal epistemic outcome as far as explanation is concerned. Suppose, then, that everything else is held equal between a set of rival hypotheses: the costs of pursuing them are the same, we regard it as equally likely that pursuing them would give us reliable evidence for or against them, all other expected epistemic outcomes of pursuing them are equal, and so on. In this case, assuming the decision-theoretic approach to pursuit worthiness defended in Chapter 2, scientists would be justified in pursuing the most explanatory hypothesis.

To illustrate this account, consider the following analogy. Suppose a team of treasure hunters know of a large treasure which could be buried on one of two islands, I1 and I2. As far as they know the treasure is equally likely to be on either island, but they only have the resources to send an expedition to explore one of them. However, they do know that due to the acidity of the soil on I2 the treasure is likely to be significantly damaged if buried there. They estimate that if the treasure is instead buried on I1, it could be worth up to twice as much as if it were buried on I2.Assume this does not give them any further information about where the treasure is, or how difficult or expensive it would be to recover. In this situation, it would be more rational, for obvious decision-theoretic reasons, to send the expedition to explore I1 rather than I2.

To spell out my argument in more detail, notice first that the epistemic goals of science include more than simply knowing as many truths as possible. As Kitcher puts the point:

Tacking truths together is something any hack can do. … The trouble is that most of the truths that can be acquired in these ways are boring. Nobody is interested in the minutiae of the shapes and colors of the objects in your vicinity, the temperature fluctuations in your microenvironment, the infinite number of disjunctions you can generate with your favorite true statement as one disjunct, or the probabilities of the events in the many chance setups

you can contrive with objects in your vicinity. What we want is significant truth (1993: 94).

There are plenty of trivial truths out there that could be discovered and at much lower cost than the hypotheses actually pursued by scientists. The value of scientific knowledge depends on other factors beyond the amount of truths known, no matter how certain these are.

Now, what other epistemic goals are important in science is not something I need a general account of here. I only need to make two assumptions: first, that it makes sense to distinguish between hypotheses in terms of their explanatoriness—which explanationists also assume—and, second, that having better explanations is in fact more epistemically valuable, all else being equal. In other words, I assume that having good explanations or achieving understanding of the world are among the goals of inquiry, an assumption which is shared by most philosophers of science and explanationists in particular.71 One way a hypothesis can be more epistemically valuable than merely being true is by being a good explanation or by increasing our understanding of one or more phenomena.

Given these assumptions, consider the situation in terms of the Simple Model of epistemic pursuit worthiness developed in Chapter 2 (Section 2.5.3). We can express the assumption that explanatoriness is one important epistemic goal as the claim that if h1 is more explanatory than h2, then u(acc(h1), h1) > u(acc(h2), h2), all else being equal.72 Notice now from equation (5) that u(acc(h), h) only occurs in one place, namely in the sum weighed by Pr(h). Since probabilities are always positive, it follows that if u(acc(h1),

71 _{E.g. Kitcher (1993: 105ff) highlights “Explanatory Progress” as a goal pursued by science beyond mere}

truth.

72 _{This is “all else being equal” since h}

2 might be more valuable in terms of other epistemic goals besides

h1) > u(acc(h2), h2) then EU(ph1) > EU(ph2), all else being equal. Thus, if h1 and h2 only differ in terms of their explanatoriness, this gives us a reason to prioritise the pursuit of the more explanatory hypothesis.

So far, this argument shows that IBE can justify pursuit if all else is equal. In other words, explanatoriness can act as a tie-breaker when deciding which hypothesis to pursue. But, more generally, it is also clear that having a high degree of explanatoriness adds to the expected epistemic value of pursuing a hypothesis and thus provides some additional reason to pursue it, although not always a decisive reason. In deciding which hypothesis to pursue, all things considered, one should weigh the explanatoriness of a hypothesis against the relevant factors along the lines discussed in Chapter 2.73 _{This is of course as}

it should be. It is analogous to the observation, made above in Section 3.3, that explanationists allow for explanatoriness to be outweighed by other reasons for the truth of a hypothesis.

Given this account of how explanatoriness justifies pursuit, the argument for why neither of the objections to explanationism pose a problem for the Peircean view is straightforward. Start with the truth-connection problem: since nothing in my account requires a connection between the explanatoriness of a hypothesis and its truth, the truth- connection problem does not arise. As argued in Chapter 2, although the likeliness or plausibility of a hypothesis is one important factor in deciding whether to pursue it, it is neither the only one nor always a positive reason for pursuit. By contrast, raising the utility of achieving a given epistemic state, whether in the Simple Model or any of the

73 _{Notice that which hypothesis to pursue is decided after fixing our estimates of all relevant factors. If we}

discover that a hypothesis is more explanatory than we previously thought, or change it to become more explanatory, this can influence our estimates of other factors. So changes, say, to the plausibility of the hypothesis may outweigh any gains in explanatoriness. Analogously, for the treasure hunters, if knowing the acidity of the soil for some reason provides additional clues about whether the treasure is likely to have been buried on the island, this needs to be taken into account.

more sophisticated models, never lowers, and in most cases raises, the pursuit worthiness of a hypothesis, all things being equal.74

Turning to the subjectivity problem, my account is compatible with a wide range of views of what makes explanatoriness valuable, including radically contextualist or subjectivist ones. First, as mentioned, my account does not to take a stand on which criteria (unification, mechanism, parsimony, etc.) characterise good explanations or on how they should be weighed against each other. Furthermore, it is possible for these criteria to vary between different times, contexts or paradigms, as Kuhn (1962/1996; 1977) argues, without there being an objective, independent fact of the matter as to which type of explanations is best. As long as the agent evaluating pursuit can distinguish hypotheses in terms of whether they (if true) would constitute better and worse explanations, this allows them to use explanatoriness as a reason for pursuit. Two agents may disagree on which criteria of explanatoriness to use, say, because they belong to competing paradigms. If we accept, with Kuhn, that neither set of criteria is objectively more correct, the Peircean view would simply say that this is a case where reasonable people can disagree about which theory is most pursuit worthy. On the other hand, if we could formulate an objectively correct standard for explanatoriness, we could use this standard to say that while both agents are acting reasonably, from their own perspective, only one of the theories is truly more pursuit worthy. Either way, the Peircean view is consistent with both contextualist and objectivist accounts of explanatoriness.

Similarly, the Peircean view is consistent with a range of different accounts of why having good explanations or understanding is valuable. One could insist that understanding is somehow objectively or intrinsically valuable. But, equally, one could

74 _{The only cases where increasing the utility of an epistemic state does not raise pursuit worthiness are (i)}

where the probability of achieving that outcome is nil and (ii) where the agent is already in that epistemic state.

hold that highly explanatory theories are valuable because they allow us to achieve other goals. These could be epistemic goals: for instance, Douglas (2009: ch. 5) argues that theories with ‘cognitive’ virtues (e.g. simplicity) are valuable because they are easier to make good predictions. Woody (2004, 2015) argues that the value of explanations consists in shaping and communicating the epistemic priorities within a given field of research. Alternatively, the value of explanatoriness could be grounded in our practical, non-epistemic goals. Kitcher (2001a: ch. 6), for example, argues that whether something counts as a ‘significant’ question depends on its relation to other significant theoretical problems. Ultimately, these significance networks bottom out in practically (politically, economically, ethically, …) significant problems. Finally, my argument is consistent with the view that the epistemic value of having good explanations is purely subjective, that it is simply a matter of “making our minds feel good”. (I do not, however, find this a particularly plausible account of the epistemic value of explanatoriness.)

I do not intend to argue for any specific account of the value of explanatoriness. Rather, this brief survey will illustrate the range of available options, all of which are consistent with the Peircean view. In each case, as long as having better explanations is in fact valued within the perspective from which pursuit is being evaluated (either an external, objective perspective or the internal perspective of the agent), explanatoriness provides a reason for pursuit. Thus, the subjectivity problem does not arise.