Scientific Explanation

1
Scientific Explanation

• Suppose we assume that explanation and prediction
  of phenomena are the goals/purposes of science
• Suppose we also assume that any account of
  scientific explanation needs to incorporate logic
  and experience
• Hempels D-N model of explanation
• D Deductive
• N Nomological (i.e., law-like)
• Hempels model is formal and deductive

2
Scientific Explanation

• E An event to be explained The water in my car
  radiator froze last night.
• How to explain this?
• (Relatively) pure water freezes at 32 degrees.
• My car radiator contains relatively pure water
  and the temperature last night was below 32
  degrees.
• --------------------------------------------------
  ----------
• Therefore, E (the water in my car radiator
  froze)

3
Scientific Explanation

• E An event to be explained The water in my car
  radiator froze last night.
• If some phenomenon, E, can be subsumed under
  law-like generalizations and initial conditions
  (i.e., derived validly from them), then that
  phenomenon is explained.
• Hempels model
• L1, L2 LN (Relatively pure water freezes)
• C1, C2 CN (My car radiator contains and the
  temp is)
• --------------------
• E

4
Scientific Prediction

• E An event predicted The water in my car
  radiator will freeze last night.
• Hempels model
• (Relatively) pure water freezes at 32 degrees (L)
• My car radiator contains relatively free water
  and the temperature tonight will go below less
  than 32 degrees (C1 and C2).
• --------------------------------------------------
  ------------------
• So, the water is my car radiator will freeze
  tonight (E).

5
Laws and causation

• The laws that function in the D-N Model of
  explanation are universal statements these are
  statements of the form whenever and wherever
  conditions F occur, then so always and without
  exception will certain conditions of another
  kind, G, occur.
• Strictly speaking, a statement will be considered
  a law only if there are reasons to think it is
  true.
• But at least some laws (Galileos and Keplers)
  would not qualify as they are known to hold only
  approximately.

6
Laws and causation

• More recently some, like philosopher/physicist
  Nancy Cartwright, have argued that all the
  so-called laws of physics are tweaked so as to
  make them fit exceptions.
• Cartwright, How the Laws of Physics Lie.

7
Laws and causation

• The account of laws (they are statements of the
  form whenever and wherever conditions F occur,
  then) needs more however to rule out
  accidental generalization
• For example, the true and universal statement
  All the rocks in this box contain iron.
• Compare it to All relatively pure water will
  freeze at 32 degrees provided the altitude isnt
  too high, the water too deep, etc.
• What makes them different (if they are)?

8
Laws and causation

• One intuition the statement about water freezing
  presumes causation that low temperature
  causes water to freeze but being in this box
  does not cause a rock to contain iron.
• The philosophical problem of causation (thanks,
  again, to Hume) all we can mean by a causes b
  is that b always follows a (constant
  conjunction)
• We experience nothing like a cement or glue
  between the occurrence of a and subsequently that
  of b.

9
Laws and causation

• What makes them different (if they are)?
• Another intuition (genuine) universal statements
  yield counterfactual conditionals, while
  accidental generalizations do not
• E.g., If my car radiator contained relatively
  pure water (though it does not) and the temp went
  below 32 degrees, that water would freeze.
• E.g., If this rock were added to box (which it
  is not), it would contain iron.

10
Laws and causation

• What makes them different (if they are)?
• Hempel we should at least note that genuine
  law-like statements can support explanations,
  while accidental generalizations cannot.
• AG All the rocks in this box contain iron.
• This rock is in this box.
• ------------------------------------------------
  
• This rock contains iron.

11
Challenges to the D-N Model

• This is not a universal account of explanation
• Some sciences include probabilistic
  generalizations from which only probable
  explanations and/or predictions follow. (Hempel
  does acknowledge this and offers a statistical
  covering law model.)
• More importantly, some sciences including
  biology do not have any laws. Are they not able
  to offer explanations?
• Historically this led some to question whether
  biology (or the social sciences) were real
  sciences

12
van Fraassens account

• Explanation is not a formal relationship (defined
  in terms of logic) between a law-like statement
  and some phenomenon
• Many scientists and philosophers now see
  understanding rather than explanation and
  prediction as the primary goal of science
• Explanation in science is a pragmatic
  relationship context and practice dependent
• Why questions are asked, and regarded as
  answered, within specific scientific contexts
• To understand them (and what will count as an
  answer) requires knowledge of the scientific
  context within which they are asked.

13
van Fraassens account

• Example Why sex?
• Reminders
• Answers will greatly vary depending on context
  (religious vs. scientific, and within different
  scientific epochs)
• For evolutionary biologists it is a question
  because
• If the name of the game is passing on ones genes
  (or reproducing oneself), sex cuts down by half
  the relevant inheritance
• It is also expensive in other ways mating
  rituals, fighting (usually among males) for
  females concerns over paternity, etc.