So truth may have many modalities or multiple methods of inquiry. Truth really just describes our willingness to ascribe a state of certainty due to an act of interpretation properly carried out. — apokrisis

Yes, this is quite consonant with the pragmatist accounts of truth endorsed by Putnam or Wiggins (See David Wiggins, (2013) Truth, Pragmatism and Morality. Philosophy 88 (3) for a recent statement of this view by way of a commentary on Putnam's account of the objectivity of ethical judgments)

It is important, though, to stress that the concept of truth entails that the act of interpretation has indeed been properly carried out by the judging agent according to a standard that is immanent to the practice of the community of thinkers who share into her practical/rational form of life.

It's interesting that, in their own different ways the philosophies of Descartes, Spinoza and Leibniz all seem to make free will impossible. — John

The main problem, for Descartes, it seems to me, it to account for the intelligibility of interactionism: how can immaterial souls have effects on material bodies. I don't see how his philosophy makes trouble for free will as such, since the orientation of the will originates in the soul and there is no indication that, for him, the activity of the soul must be governed by deterministic laws. There may be a problem with free will and divine foreknowledge, but that is quite different from the problem of free will and determinism that afflicts materialistic accounts of the mind.

As for Spinoza, his view of the mind is often characterized as a form of epiphenomenalism. If natural processes are deterministic, then he would inherit the problem of free will and determinism. This may be why he bit the bullet. He didn't envision the possibility of some sort of compatibilist solution, as Leibniz did.

It resulted from the fact that his central theses clearly ruled out free will. — Mongrel

What central theses of Leibniz do you take to be ruling out free will?

I can't really imagine how that would be the case, though. — Terrapin Station

I can't either. I was granting this possibility to Mongrel merely for the sake of argument. The conversation then moved beyond that. If we move beyond idealized "fundamental" (so called) laws of physics to the more generalized concept of a law of nature exemplified in ordinary scientific practice (including the practice of physicists) then the sort of natural necessities at issue appears quite distinct from logical necessities.

I haven't seen anything to suggest that the Leibnizian conception is really compatibilist, other than misrepresentations, like Mongrel's. I have no faith in compatibilist accounts, from what I've seen, free will and determinism are genuinely incompatible, and to make them appear compatible requires self-deception, misrepresenting one concept or the other, or both. — Metaphysician Undercover

Whether or not an account can or can't be qualified as compatibilist depends on one's conception of what it is exactly the compatibility with which free will is deemed to be problematic. This is usually taken to be determinism, but there are many varieties of determinism. The SEP article referenced earlier does qualify Leibniz's view as a compatibilit one, albeit not unqualifiedly. It is clear that Leibniz was endorsing the reality of human free will and that he was also, on many accounts, a neccessitatian, and he was unquestioningly defending a doctrine of preestablished harmony. See Clive Borst's Leibniz and the Compatibilist Account of Free Will for further discussion. (I have only parsed it obliquely, but it seems quite informative)

I think you may be right to be suspicious of mainstream compatibilist accounts (such as those of Daniel Dennett, Anthony Kenny, Susan Wolf, or of new dispositionalists such as Kadri Vihvelin or Dana Nelkin). There is much truth in most of those accounts, but the main issue with them, on my view, is that they tend to share too much of their incompatibilist or hard determinist opponents's conceptions of determinism. What seems seldom to be questioned is that the determinism as issue somehow could be a consequence of the content of the laws of physics.

On my view, the mainly empirical issue of the determinism of the laws of physics proper doesn't have much of a bearing on the metaphysical doctrine of universal determinism. That's because the possibility to derive the latter from physical determinism is questionable, often assumed without argument, or, when attempted, is seen to be relying on questionable reductionist theses, or on flawed ideas about global supervenience that are insensitive the the peculiar modal character of laws, norms and principles of animal/rational life that don't belong to physics proper. I hold universal determinism to be false, and its falsity to be knowable a priori, whatever physics may have to tell us regarding the behavior of matter.

So this is the next point, and this is what makes free will so difficult to prove. Not only must both P and not-P be logically possible, but also the free willing agent must be capable of proceeding with either one of the actions, P or not-P. If the free willist chooses P, and proceeds, the determinist will say that was determined, and if the free willist chooses not-P, the determinist will say that was determined. It is impossible for the free willist to choose, and proceed with both actions, P and not-P, so it appears impossible for the free willist to prove that one is capable of proceeding with either P or not-P. Even if the free-willist flips a coin to decide to proceed with P or not-P, this does not prove free will. — Metaphysician Undercover

This is the sort of argument that I have been attempting to address in this post and this post, which appeared below the post you were replying to.

Sue was born and continues to live with hunger and needs of various kinds. These facts account for most of Sue's whereabouts and situational posturing. Whether her deliberation has any bearing on her location is broadly speaking the very issue under discussion. — Mongrel

It would be a rather crude and philosophically uninformed stance, one informed maybe by some form of physical reductionism, or by Watsonian behaviorism, to acknowledge that hunger has some bearing on the explanation of Sue's behavior while denying that the structure of her deliberative powers can have any such bearing. That is not the nature of the contemporary philosophical debate about free will. Hard determinists who are skeptical about the possibility of free will rather argue that Sue wasn't free in spite of the acknowledged causal/explanatory role of her deliberations. That's because they believe any such episode of cognitive deliberation to be the manifestation of an underlying deterministic process that isn't consistent with her having the ability to do otherwise. This is basically the argument that I have tried to show to be flawed.

If B (a set of spaciotemporal specifications), then A (where A is a statement of natural law.) — Mongrel

Laws can't be derived logically from mere sets of empirical observations. If all ravens are black, that doesn't make it a law that all ravens are black, for it may be an accident that all ravens are black. (This is a point famously belabored by Hume). If, on the other hand, it is a law that ravens are black, then this may explain why all (or most) ravens are black. The law would derive from some features of the nature of ravens (i.e. the specific form of life they exemplify) that explain why they come to grow black feathers in normal circumstances. Those contingent circumstances, as well as the contingent circumstances of the past evolution of this life form, would explain this biological law. This would be an example of a contingent biological law about ravens.

Now, it is not within the power of ravens to modify the (contingent) circumstances that account for its being a (contingent) law that they grow black feathers in normal circumstances. If, on the other hand, it follows from some set of laws of physics that Sue -- a mature rational human being -- must do A in situation C, then, if Sue additionally had some intelligible reason to do A, it is usually as a result of Sue's exercise of her rational powers of practical deliberation that she found herself in a situation C such that the laws of physics ensure that she would decide to do A. From the point of view of the laws of physics, which have nothing to say generally about actions of type A, it is simply an accident that the antecedent physical situation C of Sue's deliberation was such that it was physically necessary that she would decide to do A. What rather explains, and necessitate, that this antecedent physical situation was such that she would proceed to do A merely is the fact that it was rational for her to do A in the intelligible circumstances exemplified by C.

Look back at what you wrote... confusing the concepts of conditional and contingent. — Mongrel

That was a bit of a shorthand but I thought the context made it clear what I meant with the phrase "... depends contingently on ..."

If A depends conditionally on C, and C is contingent, then A inherits it contingency from C's contingency even if the law that expresses the conditional dependence is necessary. Hence, if physical laws make it (physically) necessary that I would do A in conditions C, but C is a contingent set of conditions, then it may still be contingent that I am doing A. The key for understanding compatibilist free will is that the relevant contingent conditions of the action aren't outside of the scope of the powers of human beings, but are partially determined by them in accordance with our rational second-natures -- that is, in accordance with our acquired sensitivity to the reasons that we may have for acting in this or that way in relevant circumstances.

Also the suggestion that I am appealing to pure modal logic in order to provide a foundation for "volition" (a loaded philosophical term that I never even make use of) is unwarranted. I am merely making use of modal logic in order to clarify the structure of the argument as best as I can.

It looks to me like you've built an edifice of complete absurdity. — Mongrel

What is absurd? You seem to equate actuality with necessity, and I can understand that from such a point of view the very idea of unactualized powers (in general, or unactualized powers of human agency in particular) can seem absurd. Likewise, from the point of view of radical skepticism, perceptual knowledge of the external world may seem absurd. But from a common sense perspective the notions that I am defending against philosophical prejudice are truisms rather than absurdities. It is rather the dogmatic assimilation of actuality and necessity, without argument, that is absurd.

The concept of natural law isn't without its critics. Having to point out when and where a rule applies isn't much of a threat, is it? — Mongrel

It means that whether or not such a law applies here and now depends on the surrounding conditions here and now. The applicability of this law (and hence the validity of its status as a law) depends contingently on the local conditions. The apparatus of modal logic thus applies where "possible worlds" range over the attainable variations in local conditions. A "compatibilist" about free will can define possibilities for action as possibilities within such a range of contingent conditions. Human agents have both the power to do A, and to abstain to do A, just in those cases where the actual conditions determining whether or not they do A were set by the agent herself, and can thus be traced to her reasons for acting.

It may nevertheless appear that, in case where the actual conditions of the agent are C, and it is a law that the agent does A in conditions C, that the agent didn't have the power to abstain from doing A. But this is a mistake since it is no accident why the agent found herself in conditions C, such that she would "necessarily" (i.e. from physical necessity) do A in the actual circumstances; it is precisely because she had a reason to do A in those circumstances that her conditions were set to C (as a result of the normal functioning of her cognitive abilities and of her underlying physiology). If she had had reasons to abstain from doing A, counterfactually, then her conditions would also have been different and it is her power to abstain from doing A that would rather have been actualized.

Obviously what happens in a black hole stays in a black hole. We were talking about whether the whole universe could have been different. — Mongrel

We were also talking about the meaning of "could have been different". I don't know what the point of your comment about black holes is. Some natural laws of insular ecology apply only to island ecosystems and some natural laws of chemistry apply only to aqueous solutions in thermodynamic equilibrium. That's the sort of locality I was referring to. The relatively broader range of applicability of the "fundamental" (so called) laws of physics proper just is a matter of degree, and also a matter of their abstracting away most (thought not all) the substantial-formal features of the material objects talked about. This is what makes them look like (unrestricted) universally quantified statements rather than like attributions of constitutive (albeit fallible) natural powers to contingently existing natural substances.

I was talking about intensional vs extensional difference. — Mongrel

OK, yes, if the laws of physics were logically necessary, unbeknownst to us, then the difference between the two concepts of necessity (physical or logical) would show up merely in intensional contexts of belief attribution.

As Tom as alluded to, though, and as some philosophers of science (e.g. Marc Lange) have argued, many natural laws are contingent if only because they are merely locally valid within specific sub-regions of the world (or 'quantum multiverse'). The concept of a physical law being valid only if it has the form of a true unrestricted universally quantified statement is questionable. This concept doesn't capture the way laws of nature are conceived of in actual scientific practice and it misconstrues the logic of ceteris paribus clauses. It is a concept that sneaks in contentious reductionist assumptions regarding material constitution.

Maybe a Hesperus/Phosphorus type of difference. — Mongrel

Not quite the same. The necessity of identity is metaphysical, it is neither logical nor physical.

Anyway, for the discerning eye, we just affirmed that the answer to the title of the thread is:

YES.

No, its not a matter of faith since even if one were agnostic regarding the sort of necessity that attaches to physical laws, and even if those laws were deterministic, compatibilists would not be worried about it. Conversely, hard determinists would deem us to be unfree even if the laws of physics were contingent. The impossibility for one not to be constrained by the laws of physics, and/or by the past state of the universe, are irrelevant to the existence of compatibilist free will or to the hard determinist's denial of the existence of free will.

What do you know about the natural history of the universe that no physicist currently does? — Mongrel

Physicists investigate empirical laws of physics. They don't know them to be logically necessary. We may suppose, if you like, that, unbeknownst to us, those laws are logically necessary. In that case, the concepts of logical possibility and physical possibility would be co-extensive. But they still are different concepts since, for all we know, the laws of physics possibly are not logically necessary. (Not that "for all we know ... possibly ..." is an epistemic modal notion: yet another concept of possibility that isn't equivalent to logical necessity).

The universe could have been some other way. — Mongrel

Well sure. Either the universe could or could not logically have been any other way that the way it actually is. Only in the case where it could not logically have been any other way than the way it actually is do the concepts of logical and physical necessity collapse into one. In that case, everything that is actual is logically necessary and nothing that isn't actual is logically possible. This would be the case if and only if the laws of physics, and also the boundary conditions of the universe (the "initial state") were uniquely derivable from the laws of logic (propositional logic? first order predicate logic?). But why would anyone assume this?

If physical law is necessary, then the set of all physical possibilities is the same as the set of all logical possibilities. Right? — Mongrel

No. If physical laws are logically necessary then the set of all physical possibilities is the same as the set of all logical possibilities.

Drop the issue of entailment. It's irrelevant. All that's required for statements of physical law to be necessarily true is that it's true that the universe couldn't have been any other way.

Rather, what is required for statements of physical law to be logically necessarily true is that that the universe couldn't logically have been any other way. You haven't given any indication as to why you think the world could not logically have been different than it actually is.

Your attempt at demonstrating that physical and logical necessity are co-extensive relies on your using "necessarily" equivocally as if there were just one kind of necessity. This is question begging. Of course if you assume that the world can't logically be any other way than the way (actual) physical laws specify it to be, then those two sorts of necessity collapse into one.

So what are we talking about now? — Mongrel

You had issued a challenge for me to show "what properties physical possibilities have that logical possibilities don't or vice versa." I was merely responding to this challenge. It may not be physically possible for you to jump 10 feet high right now, but unless the physical laws that account for you not having this ability can be derived from logical laws, and hence aren't contingent, then it is logically possible that you would do so.

So if physical law is necessary, then the set of physical possibilities has the same members as the set of logical possibilities. Is that what you're saying? — Mongrel

Rather, only if universally quantified statements that express physical laws are logically necessary does logical possibility entail physical possibility. But it is commonly regarded that the laws of physics aren't logical laws, and hence that something can be physically necessary that isn't logically necessary. You have offered no reason to think that the laws of physics are logically necessary.

If A and B have the same properties, A=B. Show what properties physical possibilities have that logical possibilities don't or vice versa. — Mongrel

Some empirical proposition P is physically impossible if its truth is ruled out by physical law. But if the physical law is contingent, then the truth of the proposition P is logically possible. It could have been true if the physical laws had been different. Only if all actual physical laws are deemed to be logically necessary does the logical possibility of P entail the physical possibility of P. This would mean, of course, that the truth of physical laws could in principle be inferred from pure logical analysis, which few philosophers believe to be the case.

There is neat explanation of Leibniz's compatibilist account of free will in this SEP article. The discussion of Caesar crossing the Rubicon makes it clear why Mongrel's unqualified identification of Leibnizian freedom with mere logical possibility is too quick. Caesar is free to cross the Rubicon or to refrain to cross the Rubicon (i.e. it is possible for him to do both, in the sense of possibility relevant to freedom) if there isn't anything in Caesar's nature that makes it necessary that he would choose either options. Only if you accept Leibniz's metaphysics of substances, where individuals possess "complete individual concepts", and if you thereby rule out "possible worlds" where an individual acts in a way that contradict its individual essence, can you equate "logical possibility" with physical or metaphysical possibility, or so it seems to me.

On edit: actually, reading further into the SEP article, it seems that logical possibility isn't sufficient for freedom, according to Leibniz; one also needs to act in accordance with one's complete individual concept (as determined by God -- who ensured that the best possible world was actualized) and this actuality is certain albeit logically contingent. See the last paragraph in section 4 of the SEP article linked above.

... If the human being cannot impose any restrictions whatsoever, on the external world, in what sense can you say that it has free will? To have free will, it must be logically possible that P, or not P, thus the human being must be capable of imposing the necessary restrictions to make this logically possible. The human being cannot make "P or not P" logically possible simply by asserting that it is logically possible, or else I could make it logically possible to grab a hold of the sun, by asserting that it is logically possible to do such. — Metaphysician Undercover

Do you take this to be an objection to the Leibnizian conception of freedom, specifically, or to compatibilist accounts of free will generally? I myself don't accept accounts of either kind mainly because of the Kantian objection that I mentioned. It is not sufficient for one to be free in the sense that is relevant for the possibility of genuine agency and responsibility that the principle of the action of the agent be "internal" to her (in the manner compatibilists usually understand "internal" to relate to desire or motivation). The source must also be rational/intelligible rather than merely natural/mechanical. Further, I don't take the possibility of rationally intelligible actions to be consistent with universal determinism.

You disagreed with me while saying exactly what I said. Neat trick, Pierre. — Mongrel

I didn't disagree. I said your characterization was a bit too thin. Logical possibility isn't equivalent to opportunity for action in general, but it may be construed as being similar within a highly qualified Leibnizian metaphysical framework. Teasing out unstated assumptions for the sake of clarity isn't a "trick". I'm glad that you are agreeing, though.

I could choose to do something which is logically possible, but physically impossible, such as I might decide to grab a hold of the moon, or the sun, and bring it into my house with me. This demonstrates that what really determines what is and is not possible is something other than logic. — Metaphysician Undercover

Yes, that's right. I think Mongrel's characterization of Leibniz's view may be a bit too thin. Leibniz viewed human freedom as autonomy. Some agent A is free to see to it that P (where P is a timeless proposition -- for instance the proposition that A has eaten a piece of chocolate cake at time t) if whether or not P is true is determined by A and by nothing else. This means that nothing besides the internal states of the agent much be such as to determine the truth of P. We can phrase this through saying that the condition for A, as some time t, to be free (with respect to some outcome P), is if, given the state S of the external world at t (excluding the internal state of A) then it is logically consistent with S both that P or that not P. It is fair to construe this as entailing physical possibility, meaning that for some proposition to be physically possible from the standpoint of an agent is for the truth of this proposition to be logically consistent with S. The logical possibility at issue in Leibniz's conception of free will would thus be a conditional possibility: it is conditional on the logical restrictions imposed on future states of the world by the past and by physical laws. (In Leibniz's peculiar metaphysical framework, such natural/physical/metaphysical restrictions derive from the condition that the world be the best possible world in the mind of God -- which would seem to make the internal state of any agent -- or metaphysical monad viewed as the soul of this agent -- determined as well. This doesn't undermine Leibniz's view of human freedom provided only we cast him as a compatibilist!)

Kant rather had a positive view of autonomy, qua rational autonomy, contrasted with Leibniz's purely negative view (construed as mere logical/metaphysical possibility, as explained above) and he derided Leibniz's view of freedom as mere freedom of the turnspit, since on Leibniz's compatibilist account, it would seem, a purely mechanical and non-rational device such as a turnspit, which moves according to its own internal physical principle, would turn out to be as free as we are.

According to relativity, whether an event is in your past or in your future is determined by your motion relative to it. — tom

Yes, for sure. This is simply a consequence of the relativity of simultaneity. But the issue of the simultaneity of spatially distant events (that are separated by a space-like interval) has little bearing on the issues of determinism or agency. One still is able to affect only events that are located within one's future light cone. Whatever is either within one's past light cone, or outside of one's light cone altogether, is beyond one's ability to control. Since the regions delimited by one's light cone (that is, the light cone centered where one is located at a given time) are invariant, there effectively remains an absolute past and an absolute future from the point of view of an observer, at any given moment of her life, independently of her state of motion.

Do you really think that we can experience an event, and therefore know that it is true, by reading about it? Reading about an event gives us information about it which is other than the information given in experiencing it. — Metaphysician Undercover

That seems to be an epistemological issue about our knowledge of the past that is quite unconnected to the topic of this thread. Myself, I think knowledge from testimony can be just as good, and oftentimes better, than knowledge acquired on the basis of perceptual experience. It is liable to be mistaken if miscommunication occurs or if the messenger lies. But there also are all sorts of ways for our senses to mislead us. This merely indicates that our abilities to acquire empirical knowledge (either through sense experience or testimony) all are fallible abilities.

If the principles of special and general relativity lead one to believe that there is no substantial difference between past and future, then we cannot say that the two are unconnected. — Metaphysician Undercover

Yes, but my view, which I have defended in my discussion with Question, is that the theory of relativity merely is a theory about the metric of spacetime (i.e. about its signature and curvature) and it has little bearing on the topics of determinism or time asymmetry. The idea that the future already 'exists' because it would be part of the timeless "block universe" is a wrong inference from relativity or from speculative theories of quantum gravity. This idea seems to me to be philosophical confusion projected back onto physical theories that are neutral about those metaphysical issues.

Let me put it this way, it is impossible to know what will happen without knowing what one will do. And, it is impossible to infer, without a doubt, what one will do, "from known present and past constraints". So it is impossible to know what will happen, simply by knowing present and past constraints. — Metaphysician Undercover

This is my point also, and it is true regardless of whatever quantum-mechanics (or special or general relativity) may tell us about physical laws. I simply am puzzled as to why you may think I would disagree with this.

You don't seem to be addressing the point. The point was that there is a fundamental difference between talking about someone's future, and talking about someone's past. By saying that we can talk about something other than someone's "immediate present", really misses the point, because I never mentioned the present, and I don't know what would be meant by someone's "immediate present". — Metaphysician Undercover

How is that a point that I am missing? How is that related to anything that was at issue in my argument with Question? I agree that there are fundamental time asymmetries in physics, in metaphysics, and in practical philosophy; and one never relates to one's past in the same way one relates to one's future. So I have no idea what your *point* is or what it is that I might have said that you disagree with. Ordinary quantum mechanics (as applied pragmatically to make predictions about the future or retro-dictions about the past) also recognizes a fundamental asymmetry since measurements yield a wave-function collapse, and there is nothing that yields a wave-function to un-collapse (baring some exotic 'quantum eraser' experiments). The "histories" of the many-histories interpretation of QM just are specific possible trajectories of individuals who make sequences of observations/measurements of their surroundings. The specific history one finds oneself in is determined post-facto. Hence, from any time-situated empirical perspective of an agent, at any given time, her *future* history isn't fully determined yet.

Again, to reiterate, my main point against Question was purely negative. Even if, in a sense, there is a formalism (Wheeler-DeWitt) that portrays the quantum-wave function of the universe (i.e. the 'multiverse') in a timeless fashion independently from any actual observation or determinate experimental setup, and this timeless perspective seems somewhat consistent with the "block universe" view of general relativity, the intelligibility of this formalism has little bearing on the issue of the determinism/non-determinism of the laws of physics that govern the evolution of the observable properties of our empirical world -- let alone on the topic of freedom and determinism.

I think they're still logical possibilities.

Say you're in a casino and you toss a die onto a craps table. As the die tumbles along, you may imagine 6 different outcomes. But you know apriori that every event has only one outcome.

If the die lands with the 2 face up, it is impossible that any other number also is. So in what sense were there 6 possibilities? Only logically. — Mongrel

It may be the case the the die, while tumbling, already is set on a deterministic trajectory such that it is merely an epistemological possibility that it might produce an outcome different than the outcome that is poised to occur. This would indeed be a possibility that merely stems from our ignorance of the detailed physical circumstances. But I think Metaphysician Undercover can have two different kinds of possibilities in mind regarding the future, both of which can be regarded as ontological rather than merely logical/epistemological. The first one is the sort of indeterminacy that stems from the indeterminacy of quantum mechanical systems that limit how much the present state of the tumbling die restricts the future outcomes. Micro-physical quantum indeterminacies can quickly be magnified onto macroscopic indeterminacies under such chaotic circumstances as the multiple tumblings of a small object in a ragged environment.

The second sort of ontological possibility, quite unrelated to the first one (in my opinion) occurs when one considers what do do among some range of options -- to see to it that P, Q, or R, say -- then one has to pre-select such options, as being worth deliberating over at all, only when they are still open options rather them being foreclosed by past and/or current circumstances. That is, one makes sure that it is presently within one's powers to see to it that any one of P, Q or R could come to be true. It is a bit of a dogma of hard-determinism that when one actually decides to see to it that P, then this reveals the alternative options to have been merely epistemic possibilities rather than them having been genuinely open ontological possibilities. But this is where the debate about free will and determinism ought to lie, and quantum mechanics (or general relativity) have little relevance to it.

Well, I suppose I could I ask the question again, what do you think causes decoherence? All you've told me is what doesn't cause decoherence, measurement. — Metaphysician Undercover

That's because nothing is traditionally regarded to "cause" the collapse of the wave-function, or decoherence to occur. Decoherence just is a branching out of the possible consistent histories of quantum systems (and their observers), from some observational perspective. Also, I am not committed to any particular interpretation of QM. I am merely bringing up the many histories view in order to show that, even of Question is right, and there exists an all-encompassing timeless view of the 'multiverse' (as represented by the Wheeler-DeWitt formalism for quantum gravity) this fact has no bearing on either the non-determinism of our empirical physical laws (e.g. as those laws loosely constrain our empirical future from our own lived embodied perspectives) or to the topic of free will and determinism.

Now, how do you propose to extend this principle to the future, such that we "experience" what may occur? — Metaphysician Undercover

That's very simple. When Ceasar crossed the Rubicon, this became a historical fact. It will remain true in the future that Caesar crossed the Rubicon -- and similarly for everything this facts entails logically or nomologically. For sure, a wide range of future events are consistent with this past fact, which is why QM is a non-deterministic theory even under the many histories (or many-worlds) interpretations. It encourages a view of the 'multiverse' (of the universe's wave-function) evolving deterministically, but my main point against Question, is that it (QM), just like general relativity, is quite consistent with the world (our empirical reality) being non-deterministic from our empirical point of view. This is so precisely because our past history is consistent with a variety of future histories. But this is only tangentially relevant to the other fact -- which you rightfully call attention to -- that the future (our future) has this additional feature that we can determine some features of it it through deciding what do do, and aren't constrained merely to stand-back and wait for quantum indeterminacies (or other epistemic or historical possibilities) to randomly resolve themselves.

Do you recognize a difference between the numerous logical possibilities of what may have occurred in the past when it is believed that only one of these possibilities is what actually occurred, and the ontological possibilities for the future, when it is believed that any one of these possibilities may actually occur? — Metaphysician Undercover

I think there is at least a fourfold distinction between logical, metaphysical, historical and epistemological possibilities (and there likely are several grades of metaphysical possibility). But you are quibbling away from my very simple point -- in initial response to your initial question -- that what is known to be actual (or epistemologically possible) from someones point of view extends further than the immediate present, such that it makes sense to speak of that person's history rather than our being constrained to talking merely of her present knowledge of her immediately present situation.

Of course there remains an essential asymmetry of past and future. From a merely theoretical/observational/passive point of view, prediction and retro-diction are very similar. When one learns, in the present, that a cat has been dead for a while, then one learns many facts about both the recent past and the nearby future. But, regarding the future only, can one know what will happen not merely through inferring it from known present and past constraints, but also through deciding what to do. Although the peculiar asymmetry that stems from this specifically agential perspective (i.e. our ability to control the future, and our inability to control the past) is relevant to the freewill and determinism issue, it is quite unconnected to anything that general relativity or quantum mechanics teaches us about the physical world, it seems to me. I think your concerns are completely different from Question's.

There seems to be some inconsistency in your choice words here, which creates ambiguity. You refer to all the "consistent histories" which we "may experience". Correct me if I'm wrong, but "histories" refers to past events which may or may not have been experienced, and it is nonsense to speak of histories which we may experience. — Metaphysician Undercover

I mean to be referring to the history of the world that we find ourselves in when we make empirical observations of any kind. It matters little for the purpose of the present discussion whether the events that are part of this history are past (inferred), presently observed, or reliably predicted. Consider the case of Schrödinger's cat. When we open the box, and find that the cat is dead, we can infer that it died more than an hour ago (because its body is stiff and cold, say), and also reliably predict that it will remain dead in foreseeable the future.

Even in those cases (most usual!) where our observations are observations of events that already are determined (as a result of the quantum wave-function of the observed system already being 'collapsed') -- such as our learning on the basis of historical documents that Caesar crossed the Rubicon -- we also are 'experiencing' (in the relevant sense) events that belong to our past history, and thus can rule out the possibility of our being part of an history in which Caesar wimped out. The past or the future aren't unknown to us just before they aren't 'directly' (meaning presently) observed by us.

What do you think could cause such a decoherence? Since our experience of time is key to our understanding of free will, then this decoherence must be of the utmost importance to this issue.

Decoherence, in the framework of the many-world (or consistent histories) interpretations of quantum mechanics, plays a role that is similar to the role played by the collapse of the wave-function (or reduction of the state-vector) in more traditional approaches such as the so called Copenhagen interpretation (which actually covers many interpretations). See the wikipedia articles on quantum decoherence and consistent histories.

Decoherence views (no-collapse), as opposed to collapse views (e.g. Copenhagen) have the advantage that they don't require actual measurements performed by intelligent agents to explain how macroscopic quantum systems become entangled and thus 'measure' each other, as it were. But they also have the inconvenience of leaving undefined the limit between the 'classical' and quantum domains. They promote a sort of a view from nowhere on quantum mechanical systems that isn't very appealing philosophically. One recent approach that has sought to overcome this limitation is Quantum Bayesianism. Michel Bitbols' work on the philosophical foundations of quantum mechanics is related to this and it directly adresses the issue of the cognition of time. But, as is the case with all of the above, however metaphysically enlightening, it has little direct relevance to the alleged problems of free will and determinism, on my view.

General Relativity mandates a stationary space-time block. All general relativists admit this. Those who do not like it, for whatever reason, are engaged in overturning GR. — tom

Einstein's theory of general relativity is a theory of gravitation that is formulated within the framework of classical physics. It is an obsolete theory, albeit empirically accurate at the macroscopic level. Everyone who seeks to harmonise GR with quantum mechanics is "overturning" GR, in a sense (just as GR itself overturned the special theory of relativity). It is better to say that the goal is to account for the empirical success of GR within the framework of QM. The Wheeler-DeWitt equation just is one step towards a quantum theory of gravitation, and there are alternative approaches (such as string theory).

No idea what you think Coherent Histories has to do with this?

Sorry, I meant to say "consistent histories". It is relevant since, as I suggested, the timeless wave-function describes a superpositions of all the consistent histories that we, as sentient observers, may experience, and hence its static nature doesn't entail determinism at the empirical level that interests us. The latter, as well as our experience of time, is a result of the decoherence of the timeless wavefunction into multiple independent consistent histories. If the laws of physics don't determine, given our own specific past history, what it is that we will experience in the future, then the mere consideration that all possible outcomes (i.e. all the outcomes not ruled out by QM) are somehow 'realized' in some coherent history or other (i.e. in some parallel 'world') is of little relevance to the issue of free will conceived as a capacity potentially exercised in one single 'world'.

They have to do this because they are experts, and they know relativity implies the block. Best of luck to them because they have met with zero success so far! — tom

Well, that is your own assessment of the situation. While general relativity on its own may suggest (rather than logically entail) something like the block universe view, quantum mechanics rather suggests that the fundamental laws of physics are non-deterministic. There also are no-collapse interpretations of QM, such as the many-world view, that may be construed as deterministic, but that would still make the evolution of individual coherent histories, as experienced by sentient observers such as ourselves, non-deterministic. The debate then turns on the question whether what we call *the* universe consists in the specific 'world' (or 'coherent history') that we are experiencing, or rather consists in the superposition of all of them (including 'worlds' or 'histories' in which we didn't evolve). In either cases, the issue would seem to have little relevance to the problem of free will and determinism. It doesn't make any contact with the compatibilism/incompatibilism debate, and it doesn't seem to conceive of nomological determinism at the correct psychological level of analysis such as to make it relevant to the possibilities of freedom of choice and action.

Secondly, even if we would grant that the "block universe" might consist in a superpositions of all the individual histories, it would still be quite unlike the classical block universe view suggested by relativity. We don't have a fully worked out quantum theory of gravitations, and QM has as much theoretical and empirical support as GR has. So, what gives? You seem to favor the block universe as a matter of personal preference and hence take GR to trump QM.

Finally, universal determinism -- either of the causal or nomological varieties -- are philosophical doctrines that can not be decided merely on the basis of physical theory. The selfsame physical theory often admits of different philosophical interpretations, some of which are usually overlooked by physicists. Kantian views of the experience of time, for instance, are usually ignored by physicists, or, when briefly considered, are dismissed on the basis of crude misunderstandings. For some exceptions to this philosophical naivety among physicists, consider Karen Barad (Meeting the Universe Midway) or Michel Bitbol (Some Steps Towards a Transcendental Deduction of Quantum Mechanics and Reflective Metaphysics: Understanding Quantum Mechanics from a Kantian Standpoint).

Which statement(s) in that article to you take to imply that the block theory is the received view? — Terrapin Station

The article indeed seems to portray the view as being, if not contestable, at least contested. While Andreas Albrecht was defending it, Avshalom Elitzur, Lee Smolin and George Ellis were arguing strongly against it. Jennan Ismael, a philosopher rather than a physicist, was only arguing that our experience of the flow of time is consistent with the block universe view.

Try this http://philsci-archive.pitt.edu/2408/1/Petkov-BlockUniverse.pdf — tom

Thanks for the reference. I'll read it carefully. At first glace, though, it seems like the author advocates his block universe view as the only possible alternative to presentism (the view that only the present exists). Although I don't endorse the block universe view, I am not endorsing presentism either. In The Fabric of Reality, David Deutsch has effectively argued against presentism, it seems to me, without thereby endorsing anything like the block universe view. I don't think either view is coherent, and both seem reliant on what Hilary Putnam has criticized as metaphysical realism. (This is a criticism that Putnam developed after he had published the paper Time and Physical Geometry Petkov discusses). So, Petkov may be arguing on the basis of a false dichotomy.

You are simply refusing to accept an inescapable consequence of our best theories. Nothing in reality has ever been discovered to contradict GR, or the standard model, both of which are time-symmetric theories.

I have not suggested that anything that we know contradicts GR (although we don't yet have a quantum theory of gravitation, and so GR is at best an incomplete theory, nothing that I said depends on GR being inaccurate at any level). Rather I am questioning the validity of your inference from the truth of GR (or from the truth of special relativity) to the idea that the block universe is a mandatory view.

This is why most scientists don't believe in free will, because it doesn't fit with what they know.

While some scientists are hard determinists, other philosophically informed scientists rather are compatibilists about the issue of freedom and determinism, so you are seemingly making another unwarranted inference. Even if the block universe view were correct, this would not entail that we must reject the reality of free will, unless one would also provide a convincing argument against compatibilism. Such arguments usually are of a philosophical nature -- relying on the conceptual analysis of the very ideas of agency, freedom and responsibility -- rather than being based on empirical physical theories that have little relevance to the elucidation of those concepts.

Newton's gravity is incompatible with special relativity: it allows action at a distance and is not Lorentz invariant. — tom

Of course not. It is rather invariant under Galilean transformations.

Whatever you might want to construct out of "gravity", it can't be a 4D spacetime block with a Lorentzian signature, and no such construction is forced upon you. Under relativity it is unavoidable.

The Lorentzian signature is a feature of the metric of spacetime, and, it is true, encourages the '4D block' picture since it does away with the idea of a unique present moment univocally defined throughout all of space (i.e. it does away with a uniquely defined space-like hypersurface). Hence, if there is no such thing as the present state of the universe, one may be tempted by the alternative idea that the universe exists, in a sense, all at once. But that still is optional. There can still be a local definition of the present, and there still remains regions of spacetime that belong to the absolute pasts and to the absolute future, from the point of view of an observer (namely: the past and future regions of the light-cone centered where (and when) the observer is located) and, if the overall laws of physics (besides Einstein's field equations) are indeterministic, then GR is a true theory and the universe still branches out. The 4D picture is still out and not forced upon you either by special or general relativity.

In short, physical determinism is an open question regardless of the truth of GR; and the falsity of physical determinism is inconsistent with the "4D block" picture.

I don't understand what argument you are trying to make, or what it is I have written that you may be disagreeing with (if anything). There is no mention of "Gödel's incompleteness theorem" (which one?) in you OP and I am unsure how you wish to connect this idea with the cogency of the "simulated universe theory", or its relevance to the thinking of logical positivists.