I was interested in exploring ideas about free will but whenever I hear/read discussion I always get confused about the definition of free will. So I said to myself, "okay, I missed the memo on the definition, I'll look that up". I look it up and the definition on google (Oxford Languages) is the following:

the power of acting without the constraint of necessity or fate; the ability to act at one's own discretion.

But this confused me further because I know there's this group known as compatibilists which argue that free will is actually compatible with necessity/fate. If the definition is to be taken this makes no sense. It reads like "This thing can exist while not existing".

So I come to stack exchange and look up discussions about what free will is and I see entries like this:

All the debate concerning free will is about the definition. What is the thing we want to call free will?

Which is confusing in a different matter with respect to the existence of compatibilists. How can you be arguing (in any interesting respect at least) that free will is compatible with determinism because it is defined as being so? This seems equally silly.

So if we're not arguing about the properties of a definition and we're not arguing about the definition, then what are we arguing about? I'm not denying that interesting discussions are happening but I'm unable to account for how interesting discussions are happening.

  • Does this answer your question? What is the rigorous definition of free will?
    – tkruse
    Commented Jun 19 at 6:31
  • Most discussions in this topic are not of general interest since they bring up nothing new.
    – tkruse
    Commented Jun 19 at 6:38
  • I would like to think a t least that this is a little different of a question because I think we're acknowledging that a universal rigorous definition doesn't exist so I'm asking how we go about talking about it. The first answer on that thread and the first answer on this thread are very different.
    – Matt Hauff
    Commented Jun 19 at 17:54
  • SMBC answers this: smbc-comics.com/comic/free-3
    – Barmar
    Commented Jul 4 at 21:07

4 Answers 4


The main thing is that, in much of the up-to-date debate, we start out with the concept/phrase "moral responsibility," and then relativize free will to that: "Free will is whatever cognitive, emotional, and/or behavioral capacity suffices for moral responsibility." This is why the definitional matter ends up not being so trivial/arbitrary: for we are not looking just at the internal consistency of one definition (which can be had with almost no effort, especially when the thing in question is supposed to be by itself so ethereal and variable that it can be made consistent with so much), but the consistency of externally separated definitions (viz., of moral responsibility and of free will).C

CI.e., we are dealing with the paradox of analysis to some extent. But analysis can be useful less in disclosing the "true" definitions of complex things, more in leading us towards the undefinable things, the building-blocks of complex definitions. This is a service well-rendered even if there are hardly any such things as "true definitions" at all.

  • This is very illuminating thank you! Are there any other goals in which the discussion gets framed? Aside from moral responsibility I mean.
    – Matt Hauff
    Commented Jun 19 at 2:41
  • @MattHauff I'm not sure... There might be questions about the structure of "reality in general" where certain definitions of free will might be used as examples or counterexamples to proposals about structures, but that is on the edge of collapsing into just-arguing-about-definitions-themselves, so I don't know. Commented Jun 19 at 6:28
  • It's also a significant part of body-mind dualism and thus spiritually relevant as "the soul"
    – tkruse
    Commented Jun 19 at 6:33

Events van habe a cause for happening and/or a reason for happening. A cause means a prior event triggering the next event. A reason means some purpose.

Lifeless nature is typically agreed in secular philosophy to happen only for causes, e.g. it rains because humidity has accumulated, not for the purpose of nurturing fields of wheat, and lack of rain (drought) does not mean a punishment of nature. This nature could mostly successfully be described by laws of nature, such as physics and chemistry, with the start of the universe being an exception.

For animate nature, in philosophy typically mostly for animals and humans, the questions is whether events also happen always for causes, or sometimes for reasons, or both at the same time.

Incompatibilism means both at the same time cannot be possible, if events are caused, no purpose could make them happen otherwise. Compatibilism means both are possible at the same time, purposes can exist and be executed via causation.

This has impact on morality and responsibility, but also any event happening without a natural cause would further require and allow an independent reality besides physical nature, the domain of the mind, which many people would love to exist, or hold to be self-evident via subjective inspection. It can also be a matter of pride, for people being proud in their belief of human exceptionalism, that humans have a special skill to escape causation of physical laws, potentially as a divine gift with some divine purpose, an external meaning of human life.


Half a cent.

Roughly speaking, those who accept (some kind of) free will are in two groups:

a) (incompatibilist) libertarians
b) compatibilists

Those who do not accept (any kind of) free will are usually:

c) (incompatibilist) determinists.

A main point of disagreement between a) and b) is whether (strict) determinism holds, and specifically about the ability to do otherwise under same conditions.
Note that libertarians do not, in principle, deny that partial determinism indeed holds; they simply point out that: i) there are reasons strict/total determinism cannot hold and, ii) science actually only supports, and is only compatible with, partial determinism (up to now).

In summary, it is argued that, ability to do otherwise is a necessary feature of having free will, the kind of free will we normally recognize as having, and denying it (eg as determinists do), or making it impotent (eg as compatibilists do), provides for no free will at all, in the final analysis.

A discussion on a),b),c) positions and defense of libertarian free will can be found in: A rationalist argument for libertarian free will

In this thesis, I give an a priori argument in defense of libertarian free will. I conclude that given certain presuppositions, the ability to do otherwise is a necessary requirement for substantive rationality; the ability to think and act in light of reasons. ‘Transcendental’ arguments to the effect that determinism is inconsistent with rationality are predominantly forwarded in a Kantian manner. Their incorporation into the framework of critical philosophy renders the ontological status of their claims problematic; rather than being claims about how the world really is, they end up being claims about how the mind must conceive of it. To make their ontological status more secure, I provide a rationalist framework that turns them from claims about how the mind must view the world into claims about the ontology of rational agents. In the first chapter, I make some preliminary remarks about reason, reasons and rationality and argue that an agent’s access to alternative possibilities is a necessary condition for being under the scope of normative reasons. In the second chapter, I motivate rationalism about a priori justification. In the third chapter, I present the rationalist argument for libertarian free will and defend it against objections. Several objections rest on a compatibilist understanding of an agent’s abilities. To undercut them, I devote the fourth chapter, in which I give a new argument for incompatibilism between free will and determinism, which I call the situatedness argument for incompatibilism. If the presuppositions of the thesis are granted and the situatedness argument works, then we may be justified in thinking that to the extent that we are substantively rational, we are free in the libertarian sense.


The definition you quoted is a good one. It can be simplified to simple "the ability to make decisions" without losing the meaning. The main point is that the agent decides, no-one else.

Compatibilism requires another definition for both free will and determinism. Compatibilism posits that the agent's actions are both decided by the agent and determined by prior causes.

The fact that there is no universally accepted definition for free will makes discussing free will difficult and very prone to misunderstandings. The good side of this is that all valid definitions leave no room for discussions about whether free will exists or not. Every valid definition makes it clear whether free will is a real phenomenon or an imaginary one.

No valid definition leaves the question unanswered.

  • What is a "valid definition"?
    – JMac
    Commented Jun 19 at 11:42
  • Every valid definition makes it clear whether free will is a real phenomenon or an imaginary one. It is quite pointless to define free will as a "controversial question" for instance. Either you define it as something real or as something imaginary. Commented Jun 19 at 14:37
  • What makes a definition "valid" though? You repeat this term a lot, but it's not clear to me what that means.
    – JMac
    Commented Jun 19 at 16:00
  • And I have explained it already twice. A valid definition defines exactly what is the thing that is given this name. An invalid definition is vague and raises questions. Commented Jun 19 at 17:37
  • 1
    It's hard to imagine a definition that wouldnt allow for any further questions. Typically we just make assumptions about the intended message instead of discussing semantics forever, though. And typically we define words how they are used, so if freewill is used in multiple different ways, the definition can reflect that ambiguity without taking a definite stance.
    – JMac
    Commented Jun 19 at 19:08

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