Page 171 - MODES of EXPLANATION

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My argument is that this dichotomous structure – contingent vs. naturally necessary –
is the wrong conceptual frame. Rather, there are dependencies in nature and they come in
degrees. True (logically contingent) generalizations are not all in one box or the other;
instead, there are degrees of contingency, different levels of dependency. Some structures are
more ephemeral; others are more stable. There are structures that have endured since the first
three minutes after the Big Bang and there are others that come and go. We can have
knowledge of all of these structures, but all of these pieces of knowledge are going to fit
2into the “naturally contingent” box. So having a dichotomous framework does not
give us the right tools to understand the kind of knowledge and generalizations that can
explain what occurs in our universe.
I would suggest that we should not think about laws in terms of whether they satisfy
this dichotomous strict law model; rather, we should think about them in terms of their
functions. What is it that laws do? What kinds of truths can satisfy that function?
Laws are what science allegedly looks to discover about nature. They explain why
what happens happens. They permit us to predict what will happen in the future or what
would have happened in other circumstances. They provide us with tools to intervene in the
world in order to achieve our pragmatic goals: going to the moon, building a bridge, curing
cancer. There are many truths that fulfill these functions yet fail to meet the strict notion of a
law. We can explain, predict, and intervene in the world with things that do not satisfy the
strict notion of laws.
The difference between physics and biology, or between very simple systems and
complex systems – especially complex evolved systems that display many forms of
contingencies and dependencies – is not the difference between systems that have laws and
systems that do not. Rather, the difference is one of degrees of contingency. While
generalizations that are true of fundamental physics are different from those that are true of
biological systems, the difference can be located on a continuum.
The contingency of the truths we can obtain about complex, evolved, varyingly
dependent structures indicates that explanations can be had, but that these explanations
appeal to generalizations that do not cover everything, for all times, exceptionlessly. Rather,
these explanations cover these kinds of things, under these kinds of circumstances, for these
kinds of stimuli, and so on. In order to use these “pragmatic laws” to generate explanations,
we have to have a model of explanation that does not rely on strict laws. A strict law applies
everywhere for all times; context is irrelevant. The same is not true of pragmatic laws. To
apply a pragmatic law successfully, I need to know more than merely that the relationship
being described is one between gamete production and frequency of gametes. I need to know
whether or not the contextual circumstances are ones that are generated in meiotic drive. I
need to know whether I am dealing with a sexually reproducing organism. Explanation is
going to take a different shape, but it is not going to fail to be explanatory. Such explanations
are going to appeal to laws, but not all of these will be strict laws. Some are going to be more
or less contingent laws.
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