Possible Worlds (Problems of Philosophy)

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Kastner Stuart Kauffman Martin J. Possible worlds and modal reasoning have made "counterfactual" arguments extremely popular in current philosophy. Possible worlds, especially the idea of "nearby worlds" that differ only slightly from the actual world, are used to examine the validity of modal notions such as necessity and contingency, possibility and impossibility, truth and falsity.

Information philosophy can quantify over the information in different possible worlds and thus establish the relative possibilities or "information distance" from our actual world. In ancient times, Lucretius commented on possible worlds. In his De Rerum Natura , he wrote in Book V, for which of these causes holds in our world it is difficult to say for certain ; but what may be done and is done through the whole universe in the various worlds made in various ways, that is what I teach, proceeding to set forth several causes which may account for the movements of the stars throughout the whole universe; one of which, however, must be that which gives force to the movement of the signs in our world also; but which may be the true one, De Rerum Natura , Book V, lines This is Everett's radical thesis that the observation "splits" the single observer into a superposition of multiple observers, each one of which has knowledge only of the new object-system state interpreted later by Bryce DeWitt as different "parallel universes".

In his De Rerum Natura , he wrote in Book V, for which of these causes holds in our world it is difficult to say for certain ; but what may be done and is done through the whole universe in the various worlds made in various ways, that is what I teach, proceeding to set forth several causes which may account for the movements of the stars throughout the whole universe; one of which, however, must be that which gives force to the movement of the signs in our world also; but which may be the true one, De Rerum Natura , Book V, lines The sixteenth-century philosopher Giordano Bruno speculated about an infinite universe, with room for unlimited numbers of other stars and their own planets.

This is indeed what I had to add; for, having pronounced that the universe must itself be infinite because of the capacity and aptness of infinite space; on account also of the possibility and convenience of accepting the existence of innumerable worlds like to our own; it remaineth still to prove it. I say that the universe is entirely infinite because it hath neither edge, limit, nor surfaces. But I say that the universe is not all-comprehensive infinity because each of the parts thereof that we can examine is finite and each of the innumerable worlds contained therein is finite.

There hath never been found a learned and worthy philosopher who, under any kind of pretext, hath wished to deduce from such a proposition the necessity of human action and thus to destroy free will. Thus, Plato and Aristotle among others, in postulating the necessity and immutability of God, posit no less the moral liberty and power of our free will, for they know well and understand how compatible are that necessity and that free will.

For the solution that you seek you must realize Firstly , that since the universe is infinite and immobile, there is no need to seek the motive power thereof, Secondly , the worlds contained therein such as earths, fires and other species of body named stars are infinite in number, and all move by the internal principle which is their own soul, as we have shewn elsewhere; wherefore it is vain to persist in seeking an extrinsic cause of their motion. Thirdly , these worlds move in the ethereal regions and are not fixed or nailed down on to any body, any more than is our earth, which is one of them.

And we prove that this earth doth from innate animal instinct, circle around her own centre in diverse fashion and around the sun. These matters having been thus declared, we are not, according to our principles, obliged to demonstrate either active or passive motion arising from infinite intensive force, for the moving body, as also the motor power, is infinite; moving soul and moved body meet in a finite subject, that is, in each of the aforesaid stars which are worlds.

So that the Prime Origin is not that which moveth; but itself still and immobile, it giveth the power to generate their own motion to an infinity of worlds, great and small animals placed in the vast space of the universe, each with a pattern of mobility, of motion and of other accidents, conditioned by its own nature. On the Infinite Universe and Worlds , First Dialogue The idea of many possible worlds was also proposed by Gottfried Leibniz , who famously argued that the actual world is "the best of all possible worlds.

Others included Richard Feynman. Wheeler supervised more Ph. Everett took mathematical physics classes with Eugene Wigner , who argued that human consciousness and perhaps some form of cosmic consciousness was essential to the collapse of the wave function. D thesis finally accepted in , Everett was the inventor of the "universal wave function" and the "relative state" formulation of quantum mechanics, later known as the "many-worlds interpretation.

Everett claims that every time an experimenter makes a quantum measurement with two possible outcomes, the entire universe splits into two new universes, each with the same material content as the original, but each with a different outcome.

John Bell called it "extravagant," which by Occam's Razor must be an extreme understatement. Everett described the results of a measurment by an observer.

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This is Everett's radical thesis that the observation "splits" the single observer into a superposition of multiple observers, each one of which has knowledge only of the new object-system state interpreted later by Bryce DeWitt as different "parallel universes" As soon as the observation is performed, the composite state is split into a superposition for which each element describes a different object-system state and an observer with different knowledge of it.

Only the totality of these observer states, with their diverse knowledge, contains complete information about the original object-system state - but there is no possible communication between the observers described by these separate states. Any single observer can therefore possess knowledge only of the relative state function relative to his state of any systems, which is in any case all that is of any importance to him.

Lewis, who was at Princeton in philosophy, may well have been influenced by Hugh Everett, who was at Princeton in physics, and whose meeting with Einstein motivated him to restore determinism to quantum physics. Lewis claims that Possible worlds exist and are just as real as our world.

Possible worlds are the same sort of things as our world — they differ in content, not in kind. Possible worlds cannot be reduced to something more basic — they are irreducible entities in their own right. When we distinguish our world from other possible worlds by claiming that it alone is actual, we mean only that it is our world. Possible worlds are unified by the spatiotemporal interrelations of their parts; every world is spatiotemporally isolated from every other world. Possible worlds are causally isolated from each other.

Modal realism implies the existence of infinitely many parallel universes, an idea similar to Hugh Everett III 's many-worlds interpretation of quantum mechanics. In the information interpretation of quantum mechanics, quantum systems evolve in two ways: But David Lewis is a materialist and determinist who believes that our world, the actual world, could not have been otherwise. Thus, Lewis is not a true modal realist. He insists that all his possible worlds are real and actual cf.

Hegel 's "the real is the actual". In each of Lewis's possible worlds, there are no possibilities other than the completely determined actualities.

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All of David Lewis's possible worlds are actual worlds! There are no real possibilities in any of David Lewis's possible worlds.

For information philosophy, possibilities are of course not real in the sense of actual, but are realized when they are actualized. Possibilities have the same existential or ontological status as ideas, especially multiple ideas in a mind that are evaluated as. Possible worlds and modal reasoning made "counterfactual" arguments extremely popular in current philosophy.

But counterfactuals and Lewis's counterpart theory are just language games, ways of talking, that analytic language philosophers and metaphysicians have found productive. They do have an ontological commitment to possibilities or ideas.

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Lewis appears to have believed that the truth of his counterfactuals was a result of believing that for every non-contradictory statement there is a possible world in which that statement is true. True propositions are those that are true in the actual world. False propositions are those that are false in the actual world. Necessarily true propositions are those that are true in all possible worlds. Contingent propositions are those that are true in some possible worlds and false in others. Possible propositions are those that are true in at least one possible world.

Impossible propositions are those that are true in no possible world. Saul Kripke In the 's, Saul Kripke recommended that his "possible worlds" should be regarded as "possible states or histories of the world," or just "counterfactual situations," or simply "ways the world might have been. I will say something briefly about 'possible worlds'. I hope to elaborate elsewhere. For instance, a case of circumstantial moral luck: Another person, born into a very wealthy family, does very little but has ample food and does not need to steal to get it.

Should the poor person be more morally blameworthy than the rich person? After all, it is not his fault that he was born into such circumstances, but a matter of "luck". A related case is resultant moral luck. For instance, two persons behave in a morally culpable way, such as driving carelessly, but end up producing unequal amounts of harm: That one driver caused a death and the other did not is no part of the drivers' intentional actions; yet most observers would likely ascribe greater blame to the driver who killed compare consequentialism and choice. The fundamental question of moral luck is how our moral responsibility is changed by factors over which we have no control.

Are moral facts possible, what do they consist in, and how do we come to know them?

List of unsolved problems in philosophy

Rightness and wrongness seem strange kinds of entities, and different from the usual properties of things in the world, such as wetness, being red, or solidity. Richmond Campbell [8] has outlined these kinds of issues in his encyclopedia article Moral Epistemology. In particular, he considers three alternative explanations of moral facts as: There are cogent arguments against each of these alternative accounts, he claims, and there has not been any fourth alternative proposed.

So the existence of moral knowledge and moral facts remains dubious and in need of further investigation. But moral knowledge supposedly already plays an important part in our everyday thinking, in our legal systems and criminal investigations. What are numbers , sets , groups , points , etc.? Are they real objects or are they simply relationships that necessarily exist in all structures? Although many disparate views exist regarding what a mathematical object is, the discussion may be roughly partitioned into two opposing schools of thought: This dispute may be better understood when considering specific examples, such as the " continuum hypothesis ".

The continuum hypothesis has been proven independent of the ZF axioms of set theory , so within that system, the proposition can neither be proven true nor proven false.

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A formalist would therefore say that the continuum hypothesis is neither true nor false, unless you further refine the context of the question. A platonist, however, would assert that there either does or does not exist a transfinite set with a cardinality less than the continuum but greater than any countable set. Related to the quarrel of universals, the principle of individuation is what individuates universals. Otherwise known as the " paradox of the heap", the question regards how one defines a "thing. If so, is it still a bale of hay if you remove another straw?

If you continue this way, you will eventually deplete the entire bale of hay, and the question is: While this may initially seem like a superficial problem, it penetrates to fundamental issues regarding how we define objects. This is similar to Theseus' paradox and the Continuum fallacy. The paradox runs thus: There used to be the great ship of Theseus which was made out of, say, parts. Each part has a single corresponding replacement part in the ship's storeroom.

The ship then sets out on a voyage. The ship sails through monster-infested waters, and every day, a single piece is damaged and has to be replaced. On the hundredth day, the ship sails back to port, the voyage completed. Through the course of this journey, everything on the ship has been replaced. So, is the ship sailing back home the ship of Theseus or no? If yes, consider this: Is this the ship of Theseus or no?

If no, let us name the ship that sails into port "The Argo". At what point during the journey did the crew of the Theseus become the crew of the Argo? And what ship is sailing on the fiftieth day? If both the ships trade a single piece, are they still the same ships? This paradox is a minor variation of the Sorites Paradox above, and has many variations itself. Both sides of the paradox have convincing arguments and counter-arguments, though no one is close to proving it completely. People have a pretty clear idea what if-then means. In formal logic however, material implication defines if-then, which is not consistent with the common understanding of conditionals.

If it could, then on a given Saturday, so could the statement. Formal logic has shown itself extremely useful in formalizing argumentation, philosophical reasoning, and mathematics. The discrepancy between material implication and the general conception of conditionals however is a topic of intense investigation: Grice , that no discrepancy exists.

The mind—body problem is the problem of determining the relationship between the human body and the human mind. Philosophical positions on this question are generally predicated on either a reduction of one to the other, or a belief in the discrete coexistence of both. This problem is usually exemplified by Descartes, who championed a dualistic picture. The problem therein is to establish how the mind and body communicate in a dualistic framework. Neurobiology and emergence have further complicated the problem by allowing the material functions of the mind to be a representation of some further aspect emerging from the mechanistic properties of the brain.

The brain essentially stops generating conscious thought during deep sleep; the ability to restore such a pattern remains a mystery to science and is a subject of current research see also neurophilosophy. This problem actually defines a field, however its pursuits are specific and easily stated. Firstly, what are the criteria for intelligence? What are the necessary components for defining consciousness? Secondly, how can an outside observer test for these criteria? The " Turing Test " is often cited as a prototypical test of intelligence, although it is almost universally regarded as insufficient.

It involves a conversation between a sentient being and a machine, and if the being can't tell he is talking to a machine, it is considered intelligent. A well trained machine, however, could theoretically "parrot" its way through the test. This raises the corollary question of whether it is possible to artificially create consciousness usually in the context of computers or machines , and of how to tell a well-trained mimic from a sentient entity.

Important thought in this area includes most notably: A related field is the ethics of artificial intelligence , which addresses such problems as the existence of moral personhood of AIs, the possibility of moral obligations to AIs for instance, the right of a possibly sentient computer system to not be turned off , and the question of making AIs that behave ethically towards humans and others. The hard problem of consciousness is the question of what consciousness is and why we have consciousness as opposed to being philosophical zombies. The adjective "hard" is to contrast with the "easy" consciousness problems, which seek to explain the mechanisms of consciousness "why" versus "how", or final cause versus efficient cause.

The hard problem of consciousness is questioning whether all beings undergo an experience of consciousness rather than questioning the neurological makeup of beings. Intuitively, it seems to be the case that we know certain things with absolute, complete, utter, unshakable certainty. For example, if you travel to the Arctic and touch an iceberg, you know that it would feel cold. These things that we know from experience are known through induction. The problem of induction in short; 1 any inductive statement like the sun will rise tomorrow can only be deductively shown if one assumes that nature is uniform.

Thus induction cannot be justified deductively. Popper attributes this problem to Kant. Although Popper mentions mathematics and logic, other writers focus on distinguishing science from metaphysics. Does a world independent of human beliefs and representations exist? Is such a world empirically accessible, or would such a world be forever beyond the bounds of human sense and hence unknowable? Can human activity and agency change the objective structure of the world?

These questions continue to receive much attention in the philosophy of science. A clear "yes" to the first question is a hallmark of the scientific realism perspective. Philosophers such as Bas van Fraassen have important and interesting answers to the second question. In addition to the realism vs. With respect to the third question, Paul Boghossian 's "Fear of Knowledge: Against Relativism and Constructivism". Harvard UP, constitutes a more moderate critique of constructivism, which usefully disambiguates confusing polysemy of the term "constructivism. Does philosophical progress occur?

Is it even possible? Molyneux, which he was pleased to send me in a letter some months since; and it is this: Suppose then the cube and sphere placed on a table, and the blind man be made to see: For, though he has obtained the experience of how a globe, how a cube affects his touch, yet he has not yet obtained the experience, that what affects his touch so or so, must affect his sight so or so; or that a protuberant angle in the cube, that pressed his hand unequally, shall appear to his eye as it does in the cube.

This I have set down, and leave with my reader, as an occasion for him to consider how much he may be beholden to experience, improvement, and acquired notions, where he thinks he had not the least use of, or help from them. And the rather, because this observing gentleman further adds, that "having, upon the occasion of my book, proposed this to divers very ingenious men, he hardly ever met with one that at first gave the answer to it which he thinks true, till by hearing his reasons they were convinced. Suppose that he had arrived at this point and suddenly, his eyes were opened, he recovered his view, and he crosses the entire city, making a tour of it.

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