In this post I will argue that libertarianism cannot actually explain or make rational why an agent chooses one course of action over another.  I will do this by arguing that though libertarianism seems to be able to explain why an agent acts the way she does at some given moment in time, even though the action is not causally determined, libertarianism cannot explain why the agent does that action instead of some other action.  I find this troubling, since I believe humans have free will and I believe that compatibilism is not a tenable position on free will because it collapses into hard determinism.

The main issue in the free will debate is whether or not and in what sense humans have free will.  That is, are human choices or actions free, and if so, in what sense are they free?  Both the hard and soft determinists endorse determinism, which is the view that all events (including human choices) are causally determined (necessitated) by antecedent conditions.  Humans do what they do, make the choices they do, according to both these views because of factors outside of the agent’s control, e.g., upbringing, physiology, and interactions with others.  On both views, if time were rolled back any amount and allowed to play forward again, the exact same events would occur.  The hard determinist takes this to imply that there is no free no; the soft determinist says that free will is compatible with determinism.  The libertarian position, on the other hand, denies that determinism applies to the realm of human agency.  A person’s will is causally undetermined.  According to libertarianism, if the clock were rolled back, then radically different things could happen than what happened the first time.  This is because humans could choose differently the next time around even though all antecedent conditions including beliefs and desires remained the same.

One objection that libertarianism faces is that if our wills are causally undetermined, then how can we make sense of the choices that a person makes?  The hard and soft determinists both make sense of human choice in relation to the desires and beliefs of an agent.  Bob desires to read a book and he believes there are books on the bookshelf; so he goes over to the bookshelf.  On both determinist views Bob’s desires and beliefs cause him to go to the bookshelf; the same goes for all of his other choices.  But the libertarian denies that Bob’s will is causally determined by anything; so how do we explain why Bob chose to go the bookshelf?  For we want to maintain that Bob’s choices and actions are rational—they don’t occur for no reason or randomly or arbitrarily.

The libertarian response is to say that Bob’s actions are explicable in terms of his reasons.  Here the libertarian makes a distinction between reasons as causes and reasons as goal directed intentions.  We can ask for the reason the rock fell off the cliff and we expect a causal explanation.  But we can also speak of a person’s reasons for acting in terms of her goals.  Bob goes to the book shelf in order to fulfill the purpose or goal of getting a book to read.  Nevertheless, Bob could have also chosen to ignore the goal of getting a book to read.

However, the above response does not really save libertarianism.  Imagine two parallel worlds: W₁ and W₂.  At time T₁ both worlds are exactly the same in all respects, e.g., same histories, same people, objects, etc.  Bob exists in both worlds; so we have Bob₁ and Bob₂.  Assume libertarianism is true.  At time T₂ Bob₁ goes to the bookshelf and gets a book.  We explain that choice by saying that Bob₁ had the goal of reading a book and believed books were on the bookshelf.  At time T₂, Bob₂ goes to the kitchen and gets a glass of water.  We explain that choice by saying that Bob₂ had the goal of quenching his thirst and believed water was available in the kitchen.  So Bob₁’s and Bob₂’s actions are seemingly explainable under libertarianism, despite the fact that they aren’t causally explainable, since the actions were not causally determined.

Despite the above appearance of libertarianism being able to adequately explain a person’s actions, there is the following problem for libertarianism.  We cannot make sense of why Bob₁ went to the bookshelf at time T₂ and not the kitchen, and Bob₂ went to the kitchen at time T₂ and not the bookshelf.  At time T₁ both Bobs have the same exact set of beliefs, desires, emotions, etc.  Now we can appeal to Bob₁’s goal of reading a book to explain why he went to the bookshelf and Bob₂’s goal of quenching his thirst to explain why he went to the kitchen.  However, given the details of the example, Bob₁ must also have the goal to quench his thirst at time T₁ and Bob₂ must also have the goal to read a book at time T₁.  According to libertarianism, each Bob is free to choose which goal to try to achieve.  However, since Bob₁ and Bob₂ have all of the same goals, beliefs, etc., there is nothing different between them to which we can appeal to explain why Bob₁ chose to go the bookshelf at time T₂ and Bob₂ chose to go the kitchen at time T₂.  Their individual actions are explainable, but libertarianism cannot explain why one choice is made instead of another.

The libertarian might say that Bob₂ decided that quenching his thirst was more important than reading a book, and vice versa for Bob₁.  But in virtue of what did Bob₂ make that decision?  And the same question applies to Bob₁?  Their beliefs, goals, desires, etc., are all the same.  So, neither Bob can appeal to beliefs, desires, etc., that the other does not have in order to explain the different weight given to the goals chosen, goals which are meant to explain their actions.  So under libertarianism, the decision to do one action over the other ends up being arbitrary after all.  Thus, libertarianism cannot actually explain or make rational why an agent chooses one course of action over another.