Free Will A Contemporary Introduction

Three Source Incompatibilist Arguments 147

was the compatibility of leeway freedom and determinism. This in turn can be
understood in terms of efforts either to advance or instead resist what we called
(Section 3.3) the Basic Leeway Argument for Incompatibilism (BLI), which we
shall rephrase just slightly as follows:

1. If a person acts of her own free will, then she is able to do otherwise.


2. If determinism is true, no one is able to do otherwise.


3. Therefore, if determinism is true, no one acts of her own free will.

Given the classical focus upon Leeway Freedom, the dispute over BLI amounted
to a dispute over the second premise. Now, as we explained (Section 4.1), it
seemed that classical compatibilists and classical incompatibilists were nearing a
stalemate over whether determinism is compatible with an agent’s ability to do
otherwise. It was in this context that the Consequence Argument played a pivotal
role. It at least appeared to lend substantial support to the incompatibilist side.
As we argued in Chapter 4, the soundness of the Consequence Argument is not
settled. But it is fair to say that it does help support the simple, intuitive thought
that determinism rules out the ability to do otherwise (and so rules out leeway
freedom), as BLI would have it.
While the Consequence Argument offers support to the second premise of
BLI, as explained in Chapter 5, Frankfurt’s argument against the Principle of
Alternative Possibilities (PAP) served to cast the first premise of BLI into doubt.^1
Frankfurt’s argument has been the center of so much controversy in part because
it occasions a major shift in the basic strategies for advancing both compatibi-
lism and incompatibilism. Suppose it was established that Frankfurt’s argument
is sound. This would show that leeway freedom is not required for free will and
moral responsibility. This result would render the Consequence Argument irrele-
vant to the heart of the free will debate—or at least the free will debate cast in
terms of the conditions necessary for moral responsibility.^2
But now, if Frankfurt’s Argument were to show that leeway freedom is not
essential to free will, and if it hence rendered the Consequence Argument
otiose, it would thereby make especially salient another sort of freedom that is
required for moral responsibility. This would be source freedom. Call those phi-
losophers who accept Frankfurt’s argument, or some other argument to the same
conclusion, source theorists. Source theorists contend that in theorizing about
free will, understood as a condition necessary for moral responsibility, we must
tend just to a source model of freedom and reject an account of freedom that
essentially involves the freedom to do otherwise. Leeway theorists, by contrast,
oppose Frankfurt’s argument and other arguments for the same conclusion.
They are committed to the thesis that free will requires the ability to do
otherwise.
One might at first think that source theories are the exclusive domain of com-
patibilism, since Frankfurt himself and various others following his lead used his
argument in the service of advancing a broader compatibilist thesis. But source
theories are not the exclusive domain of compatibilists. All Frankfurt’s argument