QuestionsAre we free?Liberty is opposed to constraint, not to necessity
Are we free?Free without absolute free will

Liberty is opposed to constraint, not to necessity

Hume's reconciling project; hypothetical liberty

David Hume 1711 · 1776Neither causation nor induction can be proved: custom guides us.
See profile
What it claims

Liberty and necessity are compatible: our actions can be both free and necessary, and the dispute between the two camps has been merely verbal.

Why

In human actions as in matter, the same motives produce the same conduct: necessity is only an observed regularity.

The same idea through history
Thomas Hobbes1651Being free is not being hindered from doing what one wills, even if that will has causes.
David Hume1748Hume starts from what we know about causation, then shows that the dispute about liberty and necessity is a dispute about words.
Voltaire1766Voltaire takes up the same definition: "Your will is not free, but your actions are."
In short

"Liberty is opposed to constraint, not to necessity" is an argument by David Hume (Enquiry concerning Human Understanding, section VIII (1748), 1748) on the question "Are we free?" (answer: free without absolute free will). Its claim: Liberty and necessity are compatible: our actions can be both free and necessary, and the dispute between the two camps has been merely verbal. According to AskPhilosophy's logic check (Z3 solver), the argument is valid only if one grants a premise the author leaves unstated (P5). AskPhilosophy presents 3 objections, 0 of them with a documented reply, and the original text behind each premise, checked word for word.

Enquiry concerning Human Understanding, section VIII (1748)
Valid with an implicit premise

For two thousand years people have argued over whether we can be free when everything has a cause. Hume thinks the dispute is merely verbal: all men, learned and ignorant, have always agreed about necessity and about liberty, but they never defined their words. If "necessity" is defined as experience defines it (causes regularly producing the same effects, in our actions too) and "liberty" as the power to act according to one's will, then the two go together. The opposite of liberty is not necessity: it is constraint, that of the prisoner in chains.

P1Our only idea of necessity comes from what we observe: similar objects constantly conjoined, and the mind's habit of passing from one to the other. Nothing more is found in matter.
P2These two circumstances are found in human actions: the same motives always produce the same conduct, and we draw predictions from them every day. Acts of the will are therefore "necessary" in the sense of P1.
P3Applied to voluntary actions, liberty can only mean a power of acting or not acting according to the determinations of the will: if we choose to remain at rest, we may; if we choose to move, we also may.
P4This "hypothetical" liberty belongs to everyone except prisoners in chains: so it is possessed in the very actions that are necessary in the sense of P1.
P5 · implicit premiseThe liberty at stake when we ask whether we have free will is that of P3, not a liberty that would escape causes.
Therefore liberty and necessity are compatible: our actions can be both free and necessary, and the dispute between the two camps has been merely verbal.

click a premise to reject it

If you accept every premise, logic forces you to accept the conclusion. So the debate is about the premises.
Checked by a logic solver: the premises cannot all be true while the conclusion is false.
Without the implicit premise: Without P5, here is a situation that makes the premises true and the conclusion doubtful: a man manipulated by a hypnotist acts as he wills (P3) and is predictable (P2), but we hesitate to call him free in the sense we usually mean.
The argument is valid once P5, the hidden premise, is added: the liberty that matters is the one Hume has defined. Without P5, it only shows that a certain liberty (acting as one wills) is compatible with necessity, and an opponent can reply that this is not the liberty he cares about. So the whole debate is about P5. Hume adds two arguments in its favour: if liberty is opposed to necessity (and not to constraint), it becomes a synonym of chance, which does not exist; and without a stable cause in the agent's character, no one could be praised or blamed.
Analogy. A well-regulated clock tells the time without error: it can be predicted, that is its "necessary" side. Yet there is a real difference between a clock running freely and a clock whose hand someone holds back. For Hume, liberty is that difference, not the absence of cause.

Objections

3

Each objection is a conversation: click to see who replies and where the debate stands.

Kant 1788 · attacks premise 5

Calling actions "free" because their causes are inner (our desires, our representations) is a "wretched subterfuge". Those causes themselves come from the past, and when we must act, that past is no longer in our power. This gives a "psychological" liberty, but it is physical necessity, and no moral law or responsibility remains possible.

no reply
No reply possible: objection raised in 1788, after the author's death (1776).
The debate goes on (our summary) Hume died in 1776 and could not answer the Critique of Practical Reason (1788). He did defend the opposite idea: for him, without a stable cause in the agent's character, no one could be praised or blamed (EHU VIII, 29-31). A compatibilist answers Kant that responsibility only requires that the act come from our motives and character, not that we escape all causes. Kant replies that character itself comes from the past. The debate remains open.
Thomas Reid 1788 · attacks premise 5

To be free is to have the power to produce one's own acts, so that one could also refrain from producing them: an "active" liberty. According to Reid, a motive inclines the agent but does not cause the act. If our volitions are the effect of causes going back before our birth, we are no longer the authors of our acts. This is the thesis of "agent causation" (see also Reid's argument on this site).

no reply
No reply possible: objection raised in 1788, after the author's death (1776).
The debate goes on (our summary) Reid writes after Hume (Hume died in 1776) and partly answers him. The classic compatibilist reply: saying the agent "causes" his act without being caused by anything is obscure. An act with no cause would look like chance, which Hume holds does not exist (EHU VIII, 25). Reid's followers answer that the agent is a cause of a special kind, known by experiencing it.
Peter van Inwagen 1983 · attacks the conclusion

The consequence argument. If determinism is true, our acts are the consequences of the laws of nature and events in the remote past. But what happened before we were born is not up to us, and neither are the laws of nature. So the consequences of these things are not up to us either: if determinism is true, we have no free will. The two are not compatible.

no reply
No reply possible: objection raised in 1983, after the author's death (1776).
The debate goes on (our summary) Posthumous (Hume died in 1776). Modern compatibilists answer, for example like David Lewis (1981), that one can have the power to do something which, if one did it, would make a law of nature false or change the past, without changing either the law or the past. Van Inwagen rejects this reply. Note: Hume himself does not reason this way, since he defines liberty as a conditional power (if I choose to move, I can move).
What today's voices say
Defend it
Sabine HossenfelderShe has no problem with compatibilism: define free will as you like, it is just a definition. She still concludes that free will, in the usual sense, does not exist.