The spiritual life is not a life before, after, or beyond our everyday existence. No, the spiritual life can only be real when it is lived in the midst of the pains and joys of the here and now.

--- Henri Nouwen

You need to be real enough to be believable, but you don't necessarily have to be real enough to be real. There is a distinction.

--- Bradley Whitford

Each one has to find his peace from within. And peace to be real must be unaffected by outside circumstances.

--- Mahatma Gandhi

The spiritual life is not a life before, after, or beyond our everyday existence. No, the spiritual life can only be real when it is lived in the midst of the pains and joys of the here and now.

--- Henri Nouwen

Yep, it is.

I think all the probabilities given have to be real.

Dear Ricardo, the fact that science changes every ten or twenty years means our knowledge of the world is still quite imperfect. Despite that, we eat, wear clothes, go to school, drive a car, we buy a house and a dog, and these things are real despite the fact that we do not understand them perfectly. My answer is NO. Besides, a "probability" is just that, something probable.

Best regards, Lilliana

Although this comment/response can be seem out of context, I think that Heisenberg put it irrefutably clear with his uncertainty principle, where we cannot be 100% sure of something, then we never can give all the probabilities to something even real. Although this principle is from the point of view of quantum physics, at all time that any measurements are made, there are always uncertainties. So any real element will be an approximation to it.

Yes, it is 

I have to confess that I don't understand the question ... or for that matter, some of the answers.

The phrase "that all probabilities are given" is where I get stuck.

Victor Barradas brought up something important. Heisenberg's uncertainty principle puts a limit on how close we can come to knowing something exactly. For example, if you know how fast an electron is moving with very high degree of accuracy, you will have a low degree of accuracy in knowing its location. And vice versa. But this doesn't mean that atom, and that electron, aren't real.

I'll give another more understandable example. Let's say you want to see how hot the water in a glass is. You put a thermometer in the glass to measure the temperature. But as soon as the thermometer touches the water, it will cool the water some amount. So you'll never know exactly how hot that water was.

Does this mean the water wasn't hot, or didn't exist? It just means we don't know much of anything with perfect certainty. (And do I include any religious beliefs in this? Yes, for sure.)

Dear Lilliana, can I take a small issue with what you said about science? I'm in complete agreement that our knowledge of things around us is very far from perfect. But I don't think that science "changes" every so often. More like, it builds upon itself, and grows. The Bohr atom was an approximation that holds pretty well for the smallest atoms. The idea of electrons at different energy levels, whizzing around a nucleus, bound by electrostatic forces, was essentially right. But no, the orbits are not circular, and proton, electrons, and neutrons are not the smallest particles.

So I wouldn't say "change," rather "evolve." I bring this up because I've heard more than one person claiming that studying science is pointless, because "everything you learn will be wrong soon." Far from true!

All these questions, take a book-length answers, so I will refer to a book:

Donald Gillies Philosophical Theories of Probability.  

No no no. It is not necessary for all probabilities to given. Sometimes we do not see but we believe and that is the essence of science. Otherwise who has ever seen hotness or heat before?

Dear Ricardo De la Peña Sir,

To believe in reality we must adhere with conditional probability while enjoying with reality we must follow the outcomes of joint probability.

“You have fun at the cool kids table. I prefer my spot over here with the real people.”

― Dan Pearce, Single Dad Laughing

Possible World Semantics applies the notion of of logical possibility, not statistical probability. "Possible worlds" means logically possible worlds. 

In Lewis' framework, each "possible" world represents an objective certainty. All uncertainty is subjectively defined within the context of a given world.

Can we have a reference? You are doing ontology when you assert that possible worlds are real. You are doing epistemology when you discuss certainty. Perhaps Lewis says the concept of uncertainty is world-specific, but that does not seem correct to me. I am not a Lewis scholar, though, so would like to see the text that motivates your claim.

In "On the Plurality of Worlds", Lewis' assertion that: "absolutely every way that a world could possibly be is a way that some world is", essentially states that all possible worlds are real. In his subsequent observation that "there are ever so many ways that a part of a world could be; and so many and so varied are the other worlds that absolutely every way that a part of a world could possibly be is a way that some part of some world is", Lewis indicates that worlds can be distinguished by their parts. Consequently, I can be objectively certain that my world is real, and that 'A' is a part of some world, while also being subjectively uncertain as to whether or not 'A' is a part of my world.

I do not see what work is being done by "objectively" and "subjectively."  Necessarily, any world I am in is a real world and "A" is a part of some world (for Lewis). But  ""A" is a part of my world," if true, is only contingently true. But being a contingent truth does not entail being subjective. It is objectively true that that "if "A" is part of my world, it is contingently true that "A" is part of my world," since "A" might not have been part of my world. (That last is problematic, as my world would not be the world it is if "A" is true, had "A" not been true.) Or are we talking about knowledge? If I agree with Lewis then I suppose I hold that I  know a priori that the world I am in is a real world and that what is possible is part of some real world or the other. But I cannot know a priori that "A" is part of my world. But that does not make knowing that "A" is part of my world, if it is, subjective. How is "subjective" being used? Does it have a non-standard meaning for Lewis?

I am indeed referring to knowledge. In this context, 'A' being a part of my world is not a contingent truth; it is an objective truth of which I have no knowledge, because I am not an omniscient observer in my world. Someone else in my world can possess the knowledge that 'A' is a part of our world (e.g., if that person is 'A'). It is my subjective ignorance that underlies my uncertainty about 'A' being a part of our world, not the contingency of this truth about 'A'. If I meet 'A' at some point in the future, the objective truth of 'A' in my world is not altered by the encounter, it is my subjective knowledge of that truth that changes.

According to Lewis, "...whenever two possible individuals are spatiotemporally related, they are worldmates. If there is any distance between them - be it great or small, spatial or temporal - they are parts of one single world." In other words, it is our being spatiotemporally related, not our knowledge of our mutual presence here, that identifies each part of our world as such. This world-unifying spatiotemporal relationship is what I am referring to as an objective truth, in contrast to my subjective knowledge that this relationship exists between me and each of my worldmates.

I still do not see what work is being done by the terms "objective" and "subjective." 

Note that "contingent" does not imply "not objective." The distinctions are between necessary or contingent, objective or subjective. Necessary does not imply objective, either. 

"This world-unifying spatiotemporal relationship is what I am referring to as an objective truth, in contrast to my subjective knowledge that this relationship exists between me and each of my worldmates." 

What is the difference between my having knowledge and my having subjective knowledge?

A world-unifying relationship is a relationship, not a truth. Hence it is not an objective truth. A description of the relationship can be true. Someone can assert that because the relationship exists independently of being known, it is real. If it is real, and the description of the relationship is true, then it is usual for some people to say the description (not the relationship) is objectively true. If I know it to be true, the truth I posses is called by some objective truth (though my knowledge of it is a subjective state of my mind, as is all knowledge. Objective knowledge is, ontologically, just a state of a knowing subject. But what is being indicated by saying a state of a knowing subject is subjective (subjective knowledge)? That seems redundant. And that knowing is a state of a subject has no bearing on whether the truth known is categorized as objective. But anyway, you tell me what the difference is between my having knowledge and my having subjective knowledge (assuming you are not using "subjective" to indicate my knowledge of my own mental states, my emotions, for example.) 

I thought you were using "A" for any possible state of affairs or event. But now you use "A" to refer to a person. That a person is part of my world, if true, is contingently true. That a person is part of some world is necessarily true. 

"It is our being spatiotemporally related, not our knowledge of our mutual presence here, that identifies each part of our world as such."

What? Who said the the identity of each part of our world as such has anything to do with knowledge? Not me. I am not an Idealist. 

Allow me to clarify. I am using objective and subjective to refer to observer-independent and observer-dependent, respectively. Since my original point related to objective/subjective, necessary/contingent is irrelevant to what I was saying. In this context, subjective knowledge represents your experience of your world, while objective knowledge is everything that exists in the spatiotemporal relationship that defines the world of which we are a part.

Oddly enough, I am an Idealist. Perhaps I'm just projecting.

RE:"subjective knowledge represents your experience of your world, while objective knowledge is everything that exists in the spatiotemporal relationship that defines the world of which we are a part." The expression "experience of the world" is unclear.

Do you mean, knowledge of your own mental representations of the mind-independent world is subjective knowledge?"If so, all knowledge is subjective, since you cannot know the world as it is in itself independently of how your mind represents it to you. 

"objective knowledge is everything that exists in the spatiotemporal relationship that defines the world of which we are a part." Are you denying that knowledge is a mental state that relates the knower to the thing known?  Since "everything that exists in the...." is not a mental state, for Lewis, but rather is, for example, physical states of affairs or events, why are you calling it knowledge? Also, I thought you endorsed Lewis's possible world realism. Doing that does not make sense if you are an Idealist. Note also that an Idealist will not say that objective knowledge is everything that exist...since this conflates knowing with what is known. That the objects of knowledge are mental phenomena and do not exist unperceived (Idealism) does not imply that the objects of knowledge are themselves knowledges (objective or not). You can say something exists only as some kind of knowledge, but what that means is that the object known only exists when known. It is a mental phenomenon that only exist when it stands in the relation of being known by a knowing subject. But again, since Lewis rejects Idealism....

"All knowledge is subjective, since you cannot know the world as it is in itself independently of how your mind represents it to you." My platonism requires me to disagree.

"Are you denying that knowledge is a mental state that relates the knower to the thing known?" Of course I am (that platonism again).

"Also, I thought you endorsed Lewis's possible world realism. Doing that does not make sense if you are an Idealist." I never endorsed Lewis framework, I simply referenced it because it was referenced the original question.

"Note also that an Idealist will not say that objective knowledge is everything that exist...since this conflates knowing with what is known. That the objects of knowledge are mental phenomena and do not exist unperceived (Idealism) does not imply that the objects of knowledge are themselves knowledges (objective or not). You can say something exists only as some kind of knowledge, but what that means is that the object known only exists when known. It is a mental phenomenon that only exist when it stands in the relation of being known by a knowing subject." Mine is definitely not standard idealism; it is a framework that obviously has some areas of overlap with Lewis' modal realism.

Working Paper Rational Answers from Modal Idealism - Draft

RE: "

"All knowledge is subjective, since you cannot know the world as it is in itself independently of how your mind represents it to you." My platonism requires me to disagree."

OK, but then, it requires you to disagree with Idealism, as eternal essences do not require being known to exist eternally.

And for Plato, there is no subject knowledge - all knowledge is just knowledge of forms and souls. The rest is illusion.

Sorry for the confusion, I meant platonism as simply the assertion that there are abstract objects that exist beyond physical space and time; which aligns nicely with my, admittedly unorthodox, version of idealism. Beyond that key idea, any overlap between my framework and Plato's is unintended.

"Beyond" is a spatial predicate. I assume you mean that the existence which does not imply that it has any spatial or temporal properties. It may have such properties, such as being instantiated at a location in spacetime. But it need not. OK, but I have now lost how you connect this with Lewis's possible world realism. Possible worlds, as such, are not abstract  objects, they are concrete particulars. Or they are if they are real. Now, their properties are properties that, if universal essences, exist even if the worlds do not.

OK, where does Idealism come into this? And remember what I have never gotten in all this (1) that you want to use "objective knowledge"  for a state of affairs in a possible world that exists independently of being known. (Such states of affairs are possible objects of knowledge, and being real, it is usual to say that a sentence correctly describing one is objectively true, though I find this usage causes more problems than it solves, due to a lack of symmetry between "objective" and "subjective."  And (2) that you want to use "subjective knowledge" for...what? not clear to me. Usually it refers to knowledge of any mental, hence not public.

Prof. Ricardo, if I understood you well, you say that Prof. Lewis would be saying that for something to be that something would have to be IN all possible worlds, is that correct? 

I don't think he thinks like that, actually.

I got an extract from Stanford for you:

an assertion of the form ‘a is actual’ does not indicate any special property of the individual a that distinguishes it from the objects existing in other worlds. Rather, ‘actual’ is simply an indexical whose extension is determined by the context of utterance. Thus, the referent of ‘the actual world’ in a given utterance is simply the world of the speaker, just as the referent of an utterance of ‘the present moment’ is the moment of the utterance; likewise, an utterance of the form ‘a is actual’ indicates only that a shares the same world as the speaker. The speaker thereby ascribes no special property to a but, essentially, expresses no more than when she utters ‘a is here’, understood in the broadest possible sense.

http://plato.stanford.edu/entries/possible-worlds/#Actuality

Actual it is for me if it belongs to my world, basically. 

Right. All worlds are real worlds. The actual world is the world you are in. That aside, the same object cannot exist in two worlds. What can exist in one world is a counterpart of something in another world. You exist in the actual world and you have counterparts in other real worlds that are not the actual world.