Reality is objective, not subjective. Therefore, you can remove the subjective part of "So for him, does anything even exist?" and make it: "Does anything even exist?" The obvious answer is yes. If that doesn't convince you: That person needs to exist for anything to be subjectively true or false, doesn't it? Therefore (again) true.

"Does that mean only things we can sense are real or existent?" No, see my first sentence.

"Does that mean only things we can sense are real or existent?" I bet I could sense an awful lot that doesn't exist if I merely walked down to the train station, bought whatever I could from shady-looking people, and consumed it.

"Also, how would you define non-existence?" You need a domain D for that question to make sense. A does not exist in D if and only if D = D A.

Suppose that a person ... So for him, does anything even exist?

When you say for him it implies that there is something it is like to be him, if we assume that there is no "for" to a chair or a table.

Let us change "him" to be "chair".

So for the chair, does anything even exist?

Is their a feeling relative to the chair? if there is a for then there is something that is like to be the chair. Which means that at least the chair is aware of its own existence.

So, when you presuppose this for him, you already presuppose that there is something it feels like to be him/her, to be aware of his/her own existence.

But if he/she is deprived of this awareness, then it follows that there is no for to him/her, there is nothing that feels as a for relative to him or her, in fact, this 'person' is an "it" not a "he/she", it is not even a person to begin with.

But since you used these three terms : person, for him, and he, it follows that this entity does not have zero subjectivity (like a dead body), but a subjective inner-world, albeit minimal.

So, to this person, only one thing exists : his/her thoughts.

What makes something real?

This depends on your philosophical view :

If you are an idealist, then nothing exists except this person's thoughts. And if you are a realist, then everything we know of exists.

Suppose that a person can't sense anything. He can't see, hear, feel. Nothing. So for him, does anything even exist?

The question only makes sense if the subject is assumed at least partially conscious. I assume that the question is about a human being who is unconscious of the material world but normally conscious of their own mind, so to speak.

We have also to assume that among the range of unconscious states possible, there is a mental state where the subject, while unconscious of the material world, is nonetheless able to form rational thoughts, including thoughts about existence and about what exists.

If we suppose someone merely falling momentarily unconscious at some point, it seems clear that, trivially, their idea of existence and what exists may not change at all from what it was before falling into an unconscious state.

Presumably, in most actual cases, loss of consciousness comes with a loss of the ability of the subject to form any rational thought, but that may not be true in all cases and we have to assume it is not true in some cases at least for the purpose of this question.

Thus, eschewing triviality, we have to assume a subject who either never had any conscious perception of the material world, including of their own body, and therefore wouldn't have formed ideas about existence and what exists prior to becoming unconscious; or would not be able, while unconscious, to remember ideas formed during their prior conscious life.

In the first case, it is anyone's guess whether the subject would nonetheless be able to form a rational thought at all, let alone a rational thought about existence or exiting things. It seems very unlikely.

The second case may be a bit more favourable. However, we may fall back into triviality if we assume that the subject is able to have any memory of the material world, for example what was the subject's last meal, or the fact that the subject watched the news on television the day before.

Presumably, memory of facts about the material world may carry with it the belief in the existence of the things involved in those facts, even if the subject is currently unconscious of the outside world.

Perhaps the crucial point is whether an unconscious subject, remembering nothing of the material world or indeed of their own life, could nonetheless form the idea of their own existence as a mind, so to speak.

I don't think it is possible to answer this question but at least there doesn't seem to be any good reason to assume that it is impossible.

My own experience of being conscious of at least a small part of my own usual mind while completely unconscious of the world outside, including my own body, doesn't support this, though. I think it is to be expected that most cases of unconsciousness would be similarly negative. However, any number of cases somewhat similar to mine wouldn't falsify the possibility of forming a rational thought about existence.

A related question: is it possible to remember one's abstract ideas about the world, ideas about existence in particular, while without any memory of any concrete fact such as that of a meal or of watching the news on television. I would suppose it is, although that would be somewhat infrequent. If so, I don't see why the subject could not think about existence, and in particular about the existence of their own mind.

Does that mean only things we can sense are real or existent?

I don't think so. We still don't know if space exists at all as we usually think of it. We don't sense space as such. We merely infer its existence from the way the sensible world looks to us.

Yet, I don't think many people would be prepared to claim that this proves that space, as we usually think of it, doesn't exist. All we can do is assume that our idea of space is merely a sort of mental map representing what we cannot perceive in itself. And whatever the nature of the thing causing our notion of space, I don't think the idea that space doesn't exist makes much sense.

Also, how would you define non-existence?

As the absence of existence... The hat that is on my head right now doesn't exist. Existence is whatever we think of as existence. I don't think we could possibly tease out anything more meaningful than that.

Reality is usually thought of as whatever exists at a particular time, irrespective of what we may think or perceive. There is, however, no good reason to believe that an unconscious subject couldn't, perhaps only in some very particular cases, form the rational thought of their own existence, as a mind, à la Descartes.

Let's explore this situation by changing our perspective and altering the scenario slightly.

• If they're blind, does visible light exist?

What if a blind person told you they don't believe in visible light because they've never seen it?

• If they recover and they can start perceiving things again, do they conclude reality popped back into existence just for them?

Let's say they got hit by a car and fell into a coma. They wake up in a hospital bed weeks later. The last thing they perceived was driving in a car. Do they assume reality stopped existing while they were out and then suddenly created a history when they woke up like some sort of video game?

• When you see a person in this state, are you a figment?

They can't perceive you, yet you can clearly perceive and affect them and form thoughts and ask questions about the situation. Clearly you're real. Would it be any different if the situation were reversed?

• When you fall asleep, does everyone else stop existing?


• When you wake up, do they pop back into existence?


• When I fall asleep, do you stop existing?

This is the everyday mundane version of what you're asking. At any moment billions of people are asleep, not perceiving reality (or perceiving a different one in their dreams). At the same time billions of people go about their lives.

To answer yes to your question, or any of these questions, we have to accept that one of these billions of people have a privileged place in reality; that only their subjective perception of reality matters. That reality creates itself just for them.

Even in a brain in a jar scenario there is still an objective reality, just not one you are correctly perceiving. There are things all around us we do not perceive and have almost zero practical effect on our daily lives, neutrinos have come up as an example, yet are still (to our best knowledge) real.

Interesting question that raises lot of ethical dilemmas too. If a person is cut off from sensual perception, then are they still accountable for their actions in the world they inhabit? Are they eligible for care? And so on.

But here the question is regarding the 'reality' of the world itself.
Let me try to give a perspective about this from the Indian Vedantic tradition, with a story.
This happened with a great philosopher-king called Janaka, who fell asleep and dreamt that he had taken part in a war, and fleeing from his defeated army, enters a forest, hungry and exhausted. There he begs for food from forest-dwellers, but just before he could eat the food procured after much effort, some fighting wild boars rush in and smashe his bowl away.

The king cries out in pain and with this he wakes up to find himself in his royal bed and his luxurious palace. But the shocked king has just one question on his lips, "IS THIS REAL, OR IS THAT REAL?"

No one can give a satisfactory answer, till there comes to the palace, a young, deformed boy called Ashtavakra (deformed/knotted in 8 places). He whispers to the distraught king a few words that finally calm him down.
Ashtavakra's words were, "Neither is this real, nor is that real. You are real".

The 'you' here, is the king, the consciousness that is aware, whether asleep, dreaming or awake.To extend the analogy, for the one without sensual perception, consciousness exists, because everything is contained in Consciousness. Even inanimate objects exist in Consciousness.
Yet, the world as we know it becomes RELEVANT, being built by our perception. When we lose touch with this world (metaphorically too), we continue to exist in it, but the world is not relevant anymore. To some, this might seem like unreality.

To add a footnote, Advaita Vedanta considers creation/world to be an illusion - MAYA. Everything initially is undifferentiated energy, which assumes form to contain creation.
It is the senses and the mind, which make it 'real' for individuals, in different degrees. Ultimate transcendence of existence/world happens when we evolve to a consciousness beyond that of the mind. Then we become ONE with the ground of Being.
Does the world exist after we reach transcendence?
It does. but again, the world is no longer relevant :)

PS: I know this answer raises more questions :)

I believe a real existence must be objective and demonstrable empirically or logically.
In my opinion, it is not aceptable when I said "something is real for me".

I wonder if this "person" might be bat-like or butterfly-like. Must this "person" be treated as an end and not a means? What is entailed by "personhood?" "For him" or her or it: for is sometimes used in teleological statements. See "Teleology" by Woodfield. Is this "him" then a target which is being aimed at purposefully? Can a person do targeting even if the target is never reached? Is that what it is to "be" human?

In a Psycholinguistics class a story was told about an emperor's experiment to see which language children would naturally speak if they did not hear a language spoken. They were provided with caregivers who were instructed not to speak a foreign language to the children. Of course, the children all died. Even a human foetus needs interaction. Senseless and braindead are not extremely far apart.

The question has to be analysed :

(1) what makes things real vs. mere appearances

(2) what makes things real, that is real substances vs bundles of properties, series of events ( see SEP, " substance")

(3) what makes things real/ actual vs potential entities, possibilities

(4) what makes things real, that is positive entities ( "ens reale", "entia realia" in latin ) vs negations or privations ( like shadows, holes, inabilities, deficiencies)

(5) what makes things real vs " beings of reason, entia rationis " ( objects that are " presented to the mind" without having an actual existence out of it)?

A simple answer is : what is " real" is what can either act, exert an action or undergo an action; activity and passivity are the signs of reality. In this sense only " concrete entities" are real: numbers, sets, universals can neither act nor undergo an action.

for him, does anything even exist?

The flaw in this question is that it was prepended with the phrase "for him."

Things objectively exist if he has five functioning senses.

Things objectively exist if he has zero functioning senses.

Things objectively exist if he once had functioning senses, but lost them.

The things that objectively exist will continue to exist if he regains his senses.

Things will continue to exist even if he ceases to exist altogether.

Things do not exist “for him,” “for me,” or “for you.” They just exist. They exist, even if any given individual (such as you) had never been born. Forgive me, but it’s a bit narcissistic to imply that if you had never been born, there might be some effect on the probability that Kilimanjaro (or Tokyo, or Saturn) exists.

Here is a better question: why did you imagine that the existence of things might be a function of any individual's sensory abilities, when it clearly is not?

Someone else left a comment that the universe is

largely built through an imperfect, but highly effective consensus of individual interpretations.

That’s easily disproven.

For example, exoplanets have existed for billions of years, despite the fact that no individuals had sensed their existence – let alone reached a consensus about their existence – prior to 1991.

Newtonian physics isn't obsolete. It's a very good approximations of the way that the universe works, just less accurate than Einstein's. The conceptual apparatus, such as real time being absolute, ends up being denied in the later theory. You can get all that from the physics stackexchange, e.g. here. But whether or not that means no time at all is ever absolute depends upon your metaphysics. Suffice to say that philosophers, not physicists, talk about and analyze 'reality'.

You may think of reality when someone has no sense organs analogously to relativity. They would not experience some parts of reality; yet reality, pace your question, still exists. A couple of reasons occured to me:

1. If not, every nomic event in history depends on there being humans, or something similar, to occur. That would be I think a particularly strange form of anti-realism, with strong religious overtones. I was told that no serious philosopher believes it.




2. And anyway, human life is not sufficient for anything real, and should not be seen as itself alone creating anything. It seems that biological laws such as those of evolution are not Ceteris Paribus (and perhaps even physical laws are the same), do not universally obtain whenever all other things are equal. The SEP article on causal determinism demonstrates that for any causal sufficiency, that is for something such as human life to be sufficient for anything, we need Ceteris Paribus laws, and for those to have an open ended clause limiting the conditions that would otherwise prevent the effect (ceteris paribus I would go for a beer but I have just been struck by lightening). Instead of this, the article argues we should

shake loose from the tendency to see the past as special, when
it comes to the relationships of determination, it may prove possible
to think of a deterministic world as one in which each part bears a
determining—or partial-determining—relation to other parts, but in
which no particular part (region of space-time, event or set of
events, ...) has a special, privileged determining role that undercuts
the others. Hoefer (2002a) and Ismael (2016) use such considerations
to argue in a novel way for the compatiblity of determinism with human
free agency.

In answer to your question title, philosophers usually mean 'real' to signify mind independent. Saying that nothing is real just because nothing is real and mind independent, is trivial, and not an argument. It is much better to say that life has one, perhaps unique, but not privileged, role to play in reality.