# Discussion Questions on Kitcher's Unification Theory

1. To what extent can Kitcher accept the view that explanatory asymmetries can be *accounted for* in terms of causal asymmetries? Why, according to Kitcher, don't effects explain their causes or effects of a common cause explain one another?

2. Kitcher defends what he calls, "deductive chauvinism," that scientific explanation is or should be deterministic. Yet he recognizes that phenomena in quantum mechanics are irreducibly probabilistic and, moreover, that even macroscopic phenomena may depend at least on the absence of very low probability quantum events. How can one make sense of his position?

3. (This is the example from the van Fraassen discussion questions.) Suppose two elastic bodies travelling along the same line collide. Let the initial and final velocities of the first body be v_{i} and v_{f} and the initial and final velocities of the second body be V_{i} and V_{f}, and let the two masses be m and M. The law of conservation of momentum tells us that

(a) mv_{i} + MV_{i} = mv_{f} + MV_{f},

and the law of conservation of energy tells us that

(b) mv_{i}^{2} + MV_{i}^{2} = mv_{f}^{2} + MV_{f}^{2}.

If we add a specification of the values of the masses and initial velocities, we can explain the final velocities. That is to say, if we add equations:

(c) m = m*

(d) M = M*

(e) v_{i} = v_{i}*

(f) V_{i} = V_{i}*

Then we can derive values for v_{f} and V_{f}. (Substituting the quantities specified in (c) - (f) into (a) and (b), we would have two equations in two unknowns.) Most people would regard this derivation as explaining why the two final velocities have the values that they do. But one could instead specify the values of one of the final velocities and solve for the other final velocity and for one of the masses or for one of the initial velocities (whichever specification was replaced by the specification of one of the final velocities). It is not clear whether we would regard a derivation of one final velocity, from the other final velocity, the masses, and one of the initial velocities as an explanation. It is clear that we would not regard a derivation of the initial velocities as explanatory, and it is even clearer that we would not regard the derivation of the masses as explanatory. (Indeed if somebody were to ask, "Why is the mass of this body M?" we might be inclined to reject the question.)

How would Kitcher's unification theory make sense of these judgments?

4. How are we supposed to get from an account of accepted explanations (which is what most of Kitcher's essay is concerned with) to an account of *correct* explanations?