'''Solipsisme''' er den metafysiske teori, at ens eget jeg er det eneste eksisterende jeg. Det er betegnelsen for den filosofiske anskuelsesvinkel, hvorunder verden i sig selv kun er perciperet af én enkelt person, og eksistensen af andre bevidstheder således ikke bare betvivles, men ''benægtes''.

Solipsisme bruges indenfor filosofien næsten udelukkende som en afskræmmende anklage. Således affærdiges den radikale fænomenologi ofte med, at den (under en bestemt synsvinkel) må ende i en solipsisme.

===Argumenter ''for'' solipsismen===
Argumentet bygger på den meget normale antagelse, at vi principielt er afskåret fra indblik i andres erkendelsesteoretisk synspunkt som det beskrevne og så hoppe til solipsismen som et metafysisk standpunkt. - Hvis man principielt ikke kan erkende, at solipsismen kan udelukkes, kan man jo heller ikke være sikker på at den rent faktisk er tilfældet.

===Argumenter ''imod'' solipsismen===
Et argument imod solipsisme er at teorien selv er et resultat af en absurd at en enkelt bevidsthed pludselig begynder at tro, at den er den eneste, der findes. Nogle mener desuden, at ''sproget'' netop er en måde, hvorpå forskellige bevidstheder rent faktisk kan møde hinanden. Til sidst kunne man også på baggrund af ''etiske'' overvejelser vælge ikke at tro på solipsismen: I fald der bare er én lille chance for, at der findes ''fremmedpsyker'', så ville det nemlig være etisk utilladeligt at opføre sig som om, der ikke var.

Derudover er solipsisme som teori &ndash; meget naturligt &ndash; ikke særligt accepteret socialt, fordi den jo netop benægter fællesskabets eksistens. Dette forhold kan ofte synes at være den ''egentlige'' grund til' at kun meget få mennesker (om nogen overhovedet) for alvor har hævdet solipsismen.

==Andre punkter af interesse==
Det skal desuden nævnes, at problemstillingen stadig er særdeles aktuel mht. menneskets forhold til bevise) en sådan påstand.

'''Solipsism''' (philosophical idea that "My mind is the only thing that I know exists." Solipsism is an epistemological or metaphysical position that knowledge of anything outside the The external world and other minds cannot be known and might not exist. In the history of philosophy, solipsism has served as a skeptical hypothesis.

==Explanation==

Denial of the materialist existence, in itself, is not enough to be a solipsist. Possibly the most controversial feature of the solipsistic world view is the denial of the existence of other minds. We can never directly know another's mental state. Qualia, or personal experience, are private and infallible. Another person's experience can be known only by analogy.

Philosophers try to build knowledge on more than an inference or analogy. The failure of certain knowledge may end at "I think therefore I am" (''cogito ergo sum'').<ref>[http://www.iep.utm.edu/s/solipsis.htm#H1 Internet encyclopedia of philosophy]</ref>

The theory of solipsism also merits close examination because it relates to three widely held philosophical presuppositions, which are themselves fundamental and wide-ranging in importance. These are:
# That my most certain knowledge is the contents of my own mind — ''my'' thoughts, experiences, affects, etc.
# That there is no conceptual or logically necessary link between the mental and the physical — between, say, the occurrence of certain conscious experiences or mental states and the 'possession' and behavioral dispositions of a 'body' of a particular kind (see the Brain in a vat); 
# That the experiences of a given person are ''necessarily'' private to that person. 

Solipsism is not a single concept but instead refers to several world views whose common element is some form of denial of the existence of a universe independent from the mind of the agent.

==History==
===Gorgias===
Solipsism is first recorded with the Greek 483–Roman skeptic Sextus Empiricus as having stated:

# Nothing exists;
# Even if something exists, nothing can be known about it; and
# Even if something could be known about it, knowledge about it can't be communicated to others.

===Descartes===
The foundations of solipsism lie at the heart of the view that the individual understands all psychological concepts (thinking, willing, perceiving, etc.) by analogy with his or her own mental states; i.e., by abstraction from ''inner experience''. And this view, or some variant of it, has been influential in philosophy since Descartes elevated the search for incontrovertible certainty to the status of the ''primary goal'' of epistemology, whilst also elevating epistemology to "first philosophy". However, both these manoeuvres &mdash; methodological solipsism and the primacy of epistemology &mdash; have been called into question in modern times, with Richard Rorty making particularly pointed criticisms in ''Philosophy and the Mirror of Nature''.
thumb|[[René Descartes. Portrait by Frans Hals, 1648.]]

==Varieties==
===Metaphysical solipsism===

Metaphysical solipsism is the variety of world and other persons are representations of that self having no independent existence (Wood, 295).

===Epistemological solipsism===

Epistemological solipsism is the variety of idealism according to which only the directly accessible mental contents of the solipsistic philosopher can be known. The existence of an
external world is regarded as an unresolvable question, or an unnecessary hypothesis rather than
actually false.

===Methodological solipsism===

Methodological solipsism is the epistemological thesis that the individual self and its states are the sole possible or proper starting point for philosophical construction (Wood, 295). The methodological solipsist does not intend to conclude that one of the stronger forms of solipsism is true, but rather believes that all other truths must be founded on indisputable facts about his own consciousness. A skeptical turn along these lines is ''cartesian skepticism''.

==Psychology, and psychiatry==
=== Philosophical solipsism as pathological ===
Solipsism is often introduced (for example "Philosophy made simple", by Popkin and Stroll) as a bankrupt philosophy, or at best bizarre and unlikely. Alternatively, the philosophy is introduced in the context of relating it to pathological psychological conditions. However, solipsists believe that the philosophy of solipsism is neither bankrupt, bizarre, nor pathological.

=== Solipsism syndrome  ===
Solipsism syndrome is a dissociative mental state.  It is only incidentally related to philosophical solipsism. Solipsists assert that the lack of ability to prove the existence of other minds does not, in itself, cause the psychiatric condition of detachment from reality. The feeling of detachment from reality is unaffected by the answer to the question of whether the common-sense universe exists or not. 

=== Infant solipsism ===
Developmental psychologists commonly believe that infer that others have experience much like theirs and reject solipsism (see Infant metaphysics). Solipsists assert that this rejection is not logically justified.

==Questions==
===Consequences===

To discuss consequences clearly, an alternative is required: solipsism as opposed to what? Solipsism is
opposed to all forms of realism and many forms of idealism (insofar as they claim that there is something outside the idealist's mind, which is itself another mind, or mental in nature). Realism in a minimal sense, that ''there is an external universe'' is most likely not observationally distinct from solipsism. The objections to solipsism therefore have a theoretical rather than an empirical thrust.

One consequence that is inherent to solipsism is an atomic individualist view of the world and nature. If only I matter, then other people, animals, environments only matter insofar as they impact myself.
This may be an anti-social philosophy. Language and other social mediums are taken for granted as self conceived and inherent. Maintenance of these social tools is not required, the individual need only exist, not interact with the world. Sincere solipsists are unlikely to be persuaded by such considerations; believing society to be non-existent, there is no question of being "anti social" for them.

The American eastern philosopher Alan Watts wrote extensively about this subject.

=== Plausibility ===
  
Solipsism is the position that only perception exists. The question of plausibility depends, of course, on the philosophical groundwork one chooses to use as a starting point.  Historically, Western philosophical systems have been somewhat at odds with Eastern modes of thought, and solipsism as formulated in the context of many Eastern philosophies is not seen as problematic by its practitioners (see the section '''Eastern Philosophies''', below).  

A general (Western) discussion stemming from, for example, an objectivist philosophical groundwork, can be viewed as considering whether an idea stands up to common sense or arguments of reasonableness, and is free from obvious internal logical contradictions. Solipsism is suspect on at least two grounds, in this case.

#Can one's perception, within one's mind exist without an external something to exist in, such as a biological brain?
#Does one consider all of perceptual reality as part of one's faculty of being, such as high math, music composition and other creative work which one can not consciously re-produce?
#An objection could be termed a corollary to the two above. It asks a question about the functioning of one's personal perceptions.  The solipsist cannot deny the fact that he thinks, thus going through reasoning processes about his perceptions. His consciousness is not just perceptions; it's also thinking about them. How is this possible without some mental machinery which can perform such thinking? But if such mental machinery exists independent and apart from his perceptions, this also contradicts the "perceptions only" premise. Otherwise a solipsist can define his consciousness to contain perception and thinking processes together.
 
Note, however, that there is a potential refutation to the thesis that 'perception' requires 'thinking.' If the solipsist were merely being created instantaneously from moment to moment with all memory intact and updated, he would only think he is 'thinking' — i.e., have a ''perception'' of thinking. In fact, no ''operation'' or activity has truly taken place from percept to percept (think of how the 'still' frames of a moving picture film strip  blend into the appearance of motion) — only the passage of time. But such a refutation is very vulnerable to the objection based on language (e.g. the private language argument). A solipsist who declares that he is not really thinking cannot hold that he is really speaking.

A subjective argument for the implausibility of solipsism is that it goes against the commonly observed tendency for sane adult humans in the western world to interpret the world as external and existing independent of themselves. This attitude, not always held by children, is listed by developmental psychologists as one of the signs of the maturing mind. The principle is deeply held, and well integrated with human languages and other thought processes. However, that humans think this way, even if they must think this way, does not prove something true.

=== Neuroscience ===
  
Empirical studies of the human brain suggest that the human mind is subject to many strongly held miscomprehensions of what is held by consensus to be the external and objective world. This line of thought could be extended to the claim that even if the external world is supposed to exist, the private mental world of each agent is logically that of the solipsist. A thought experiment emphasizes this point. Imagine you are in a fight to the death: If your opponent loses, will the sun rise tomorrow? Almost all people would say yes, but if ''you'' lose, will the sun rise tomorrow? The thought experiment suggests that it is not true for any agent that all minds are on an equal footing. The principle that they are is an abstraction that ignores a very important detail in the private mental life of the agent. This idea is expressed in more detail in ''What Is it Like to Be a Bat?'', by Thomas Nagel (in, for example, ''The Mind's I'' by Douglas Hofstadter).

This argument exposes a misunderstanding which constantly recurs with regard to solipsism. If it borrows a conclusion drawn from the scientific investigation of the external world, only to pull the rug from under the scientific enterprise by declaring that there is no external world, then since the solipsist is at least uncertain that brains exist, how can he draw conclusions about his mind from them? Solipsists claim that the method is proof by contradiction. If the external world does not exist, it does not exist. On the other hand if it is assumed to exist, and studied with neuroscience, it is found that the causal chains involved in perception are indirect. Solipsists paraphrase "the external world is only known indirectly" as "the external world cannot be known at all", and thereby conclude that the external world is ''either'' nonexistent ''or'' unknowable. However, "the external world cannot be known at all" is not a corollary or implication of "the external world is only known indirectly", and no scientist would make that assumption.  Almost everybody considers science as posited on the investigation of the external world.

===Last surviving soul===

Would the last person left alive after a nuclear holocaust be a solipsist?  Not necessarily, because for the solipsist, it is not merely the case that they believe that their thoughts, experiences, and emotions are, as a matter of contingent fact, the only thoughts, experiences, and emotions that can be.  Rather, the solipsist can attach no meaning to the supposition that there could be thoughts, experiences, and emotions other than their own — that events may occur or objects or people exist independently of the solipsist's own experiences. In short, the metaphysical solipsist understands the word "pain" [i.e., someone else's], for example, to mean "one's own pain" — but this word cannot accordingly be construed to apply in any sense other than this exclusively egocentric, non-empathetic one.

== Relation to other ideas ==
===Idealism and materialism===
One of the most fundamental debates in philosophy concerns the "true" nature of the world — whether it is some ethereal plane of ideas, or a reality of atoms and energy.  Idealists,<ref>[http://www.newadvent.org/cathen/07634a.htm Catholic Encyclopedia]</ref> on the other hand, believe that the mind and its thoughts are the only true things that exist.  This doctrine is often called ''subjective'' idealism.  Thoughts and concepts are all that exist, and furthermore, only 'my' thoughts and consciousness exist.  The so-called "reality" is nothing more than an idea that the solipsist has (perhaps unconsciously) created.

===Cartesian dualism===
There is another option, of course: the belief that both ideals and "reality" exist.  Dualists commonly argue that the distinction between the mind (or 'ideas') and matter can be proven by employing Leibniz's principle of the ''identity of indiscernibles''.  This states that two things are identical if, and only if, they share exactly the same qualities, that is, are indistinguishable.  Dualists then attempt to identify attributes of mind that are lacked by matter (such as privacy or intentionality) or vice versa (such as having a certain temperature or electrical charge).<ref>[http://www.newdualism.org/papers/J.DePoe/dualism.htm Dualism]</ref><ref>[http://www.newadvent.org/cathen/05169a.htm Catholic Encyclopedia]</ref> One notable application of the identity of indiscernibles was by René Descartes in his ''Meditations on First Philosophy''.  Descartes concluded that he could not doubt the existence of ''himself'' (the famous ''cogito ergo sum'' argument), but that he ''could'' doubt the (separate) existence of ''his'' body.  From this he inferred that the ''person Descartes'' must not be identical to ''the  Descartes body'', since one possessed a characteristic that the other did not: namely, it could be known to exist. Solipsism agrees with Descartes in this aspect, and goes further: only things that can be known to exist for sure should be considered to exist.  ''The  Descartes body'' could only exist as an idea in the mind of the ''person Descartes''<ref>[http://www.iep.utm.edu/d/dualism.htm Internet Encyclopedia of Philosophy on Dualism]</ref><ref>[http://www.iep.utm.edu/s/solipsis.htm Internet Encyclopedia of Philosophy on Solipsism]</ref> Descartes and dualism aim to prove the actual existence of reality as opposed to a phantom existence (as well as the existence of God in Descartes's case), using the realm of ideas merely as a starting point, but solipsism usually finds those further arguments unconvincing.  The solipsist instead proposes that their own unconscious is the author of all seemingly "external" events from "reality".

===Radical empiricism===
The idealist philosopher George Berkeley argued that so-called physical objects do not exist independently of the so-called mind that perceives them.  An item truly exists only so long as it is observed; otherwise, it is not only meaningless, but simply nonexistent.  The observer and the observed are one. Berkeley does attempt to show things can and do exist apart from the human mind and our perception, but only because there is an all-encompassing Mind in which all 'ideas' are perceived - in other words, God, who observes all.  The solipsist appreciates the fact that nothing exists outside of perception, but would further point out that Berkeley falls prey to the egocentric predicament - he can only make his own observations, and can't be truly sure that this God or other people exist to observe "reality".  The solipsist would say it is better to disregard the unreliable possible observations of alleged other people and rely upon the immediate certainty of one's own perceptions.<ref>[http://www.answers.com/topic/george-berkeley Berkeley]</ref><ref>[http://www.philosophos.com/philosophy_article_27.html Berkeley]</ref>

===Rationalism===
Rationalism is the philosophical position that truth is best discovered by the use of reasoning and logic rather than by the use of the senses (see Plato's theory of Forms). Solipsism, which holds a similar distrust for sense-data, is thus related to rationalism, and in fact may be seen as a form of extreme rationalism.

===Philosophical zombie===
The theory of solipsism crosses over with the theory of the philosophical zombie in that all other seemingly conscious beings actually lack true consciousness, instead they only display traits of consciousness to the observer, who is the only conscious being there is.

===Falsifiability===

Falsifiability in the sense of Lakatos is not a simple principle. If an agent discovers a contradiction in their own terms within their own thoughts then there is an error, but exactly which component of the mind is at fault is not clear: if (A and B) is false, then is it A or B that is false? In practice we have in our minds many beliefs, some are held more strongly than others. When an error is found the less strongly held beliefs are considered for modification or deletion first; only if no reasonable change in these is found to fix the error do we look deeper.

A weak form of epistemological solipsism states that the agent has no proof of anything beyond the senses. This can be raw observation, at the level of "I see red", "I am not aware of a proof". A stronger form states "No proof exists", this is falsifiable in as far as anything is. In order to falsify it, a proof must be provided.   

Falsificationism indicates that if the mind of the agent produces a self contradiction on its own terms, then (by definition) some error is being made. However, the error can only be located in the agent's mind as a whole. To demonstrate that one aspect (or axiom) of that mind is incorrect requires the assumption that another is correct. If the thesis is that "all entities are aspects of the mind of the agent", then to refute this it is typically required to assume the truth of an axiom that contains the effect of "there do exist things outside the mind of the agent".

According to one argument , no experiment (by a given solipsist A) can be designed to disprove solipsism (to the satisfaction of that solipsist A). However, solipsism can still be refuted by showing it to be internally inconsistent.

The method of the typical scientist is materialist: assuming that the external world exists and can be known. But the scientific method, in the sense of a predict-observe-modify loop, does not require the assumption of an external world. In common terms, a person may perform psychological test on themselves, without any assumption of an external world. The solipsistic scientist performs experiments to determine the relation between observations, without any presumption that these observations come from a source outside the mind of the solipsist. However, this account needs to be extended to include the co-operative and communitarian nature of science.

Models involving an external world may be used, but will always be purely abstract: used for their ability to predict, but being given no special ontological status.  There are, in fact, several distinct versions of instrumentally equivalent to the other, but with different ontologies. In a solipsistic science there is no strong desire to determine which is ultimately true — in effect, none of them are, but they all have utility and intuitions to offer. However, non-solipsistic science can explain why anything is ever falsified at all, since a non-mental world does not have to bend to the expectations of science.

===Minimalism===
Solipsism is a form of logical minimalism. Many people are intuitively unconvinced of the non existence of the external world from the basic arguments of solipsism, but a solid proof of its existence is not available at present. The central assertion of solipsism rests on the non existence of such a proof, and strong solipsism (as opposed to weak solipsism) asserts that no such proof can be made. In this sense, solipsism is logically related to agnosticism in religion: the distinction between believing you do not know, and believing you could not have known.

However, minimality (or parsimony) is not the only logical virtue. A common misapprehension of Occam's Razor has it that the simpler theory is always the best. In fact, the principle is that the simpler of two
theories of ''equal explanatory power'' is to be preferred. In other words: additional "entities" can pay their way with enhanced explanatory power. So the realist can claim that, while his world view is more complex, it is more satisfying as an explanation.

===Pantheism===
While solipsism is not generally compatible with traditional views of God, it is somewhat related to Pantheism, the belief that everything is God and part of God.  The difference is usually a matter of focus. The pantheist would tend to identify him- or herself as being a part of everything in reality, which is actually all God beneath the surface.  For instance, many ancient Indian philosophies advocate the notion that all matter (and thus humans) is subtly interconnected with not only one's immediate surroundings, but with everything in the universe and claim that all that one can perceive is a kind of vision, Samsara. The solipsist, however, would be more likely to put him- or herself in the center, as the only item of reality, with all other beings in reality illusions. It could be said to be another naming dispute; "The Universe" / "God" for the pantheist is "My Unconscious Mind" / "Me" for the solipsist.

===Eastern philosophies===
Thoughts somewhat similar to solipsism are present in much of self and nonsensical and arbitrary, and merely an artifact of language rather than an inherent truth.

====Zen====