Definitions - from the Harper Collins Dictionary: PHILOSOPHY, 2nd Edition, by Peter A. Angeles, ISBN 0-06-461026-8:
EGOCENTRIC PREDICAMENT 1. the apparent situation that each person can have knowledge only of his or her own experiences. One cannot get beyond one's experiences to know anything about the world as it exists apart from oneself. One cannot know anything about another's experiences as they exist to that other person. 2. all knowledge is a product of our own individual consciousness, and no knowledge is possible of anything outside our consciousness. See entries under SOLIPSISM. 3. the term was invented by Ralph Barton Perry to name the fact that we are all limited to and by our own unique and peculiar perceptive world. We cannot go beyond this world to know what the external world is like in itself, since that knowledge would inevitably have to be structured in terms of our perception.
OBJECTIVISM (EPISTEMOLOGY) 1. the theory that a world (a) exists in itself independently of and external to our comprehension of it and (b) that it is a world that we can come to know about independently of any subjective viewpoint. 2. the view that knowledge is based on factual evidence that (a) is discovered by objective methods of science and reasoning and (b) describes things as they are. 3. the view that the only meaningful (true) knowledge is that which is derived from and/or confirmed by sensory experience. Opposite to SOLIPSISM, EPISTEMOLOGICAL.
SOLIPSISM, EPISTEMOLOGICAL (from Latin, SOLUS, alone, single, sole, + IPSE, self) 1. the theory that one's consciousness (self, mind) cannot know anything other than its own content. See EGOCENTRIC PREDICAMENT. 2. one's consciousness alone is the underlying justification for, and cause of, any knowledge of the existence or nonexistence of anything at all. Contrasted with OBJECTIVISM (EPISTEMOLOGY).
SOLIPSISM, METAPHYSICAL literally, "I myself only exist"; the theory that no reality exists other than one's self. The self (mind, consciousness) constitutes the totality of existence. All things are the creations of one's consciousness at the moment one is conscious of them. OTHER things do not have any independent existence; they are states of, and are reducible to, one's consciousness.
My argument against Metaphysical Solipsism
First, let me suggest a (perhaps uneasy) truce between Objectivism and Epistemological Solipsism: Let us grant that the external world exists as it is, in and of itself, regardless of any perception or consciousness of it. Nonetheless, the "objective methods of science and reasoning" are carried out by the consciousness, within the limits of the Egocentric Predicament. Ultimately, we can only know what we allow ourselves to know, regardless of the rules of knowing by which any particular individual abides.
Metaphysical Solipsists earliest argument centered on "The Primacy of Mind," the notion that all things exist first in the Mind Of God, and are made manifest thereafter by the Will Of God. Thus, manifest matter is necessarily the lesser. By a rather long stretch of logic, the primacy of the mind of Man over manifest matter is proposed. The notion is as old as philosophy itself, but I suspect that in medieval days it became very popular as a way of allowing philosophical speculation to proceed while avoiding charges of heresy. In more "enlightened" times, the notion of the primacy of mind has been abused to give a logical cachet to self-indulgent flights of fancy.
The modernist, "scientific" solipsists argue that the Sensory Perception is incomplete, misleading. and ultimately False. The senses report Light, Color, Sound, Heat, Pressure and Odor rather than electromagnetic wave frequencies, air pressure wavelengths, molecular motion, ergs of force, or the chemical composition of aromatic molecules. The raw data received by the external sensorium is further filtered, analyzed, and interpreted by the brain, then presented to the consciousness as an arbitrarily synthesized illusion with no provable direct relationship with external reality.
There is no possible way to know if any two people actually see the same color red, perceive the exact same scent of a rose, or hear the same Middle C note on a piano. Thus, any conscious perception is wholly a construct of the mind alone, and any perception of external reality is illusory. That makes the inner Mind the only verifiable reality. Recently, populist writings on Quantum physics have added the notion of "The Observer-Created Reality" to the Solipsist's argument.
I submit that nothing has been shown to suggest that self-perception is any less incomplete, misleading, and ultimately False. The Mind does not present itself with a schematic of synaptic junctions, neurotransmitters, neuronal pulses, frequency and amplitude of brainwaves, or a myriad of other physical processes that give rise to and moderate the subjective phenomenon called "Mind." The Mind, even while conscious, is more than sufficiently vague and contradictory to make any postulate of its ultimate primacy highly suspect.
While asleep, the utterly disjointed, non-sequential, chaotic and nonsensical character of dreams is a quite fair sample of what the mind can get itself up to when it has no objective external input to occupy it.
Anyone who replicates Michael Faraday's experiments will get the same results. Anyone with the requisite mathematical skills could examine those results and derive the same wave equations as did James Clerk Maxwell. These things don't change, no matter whether or not you have heard of them, let alone what you may think of them. If two people observe the same experiment, and one's perception of light and dark is reversed, seeing white numbers on a black scale instead of black numbers on a white scale, it doesn't matter. Ohm's Law remains E=IR.
Regarding "observer created reality," I think that is partly a Scientific Conceit, and partly ill-considered Semantics.
The experimenter doesn't really interact with events at the quantum level. The experimental apparatus imposes the conditions for a detectable event. In a sense, the design, construction and operation of the apparatus may be considered interaction, but only to the extent that it limits what kind of event can possibly be detected. The experimenter doesn't really observe an event, but rather notes the several-steps-removed effects of unobservable phenomena.
For example, the sad case in the Schroedinger's Cat thought experiment: 1)nuclear decay; 2)emission of an invisible particle; 3)detection of particle by a contrived device; 4)release of poison gas; 5)cat killed by gas; 6)box containing cat opened by experimenter, letting in light; 7)reflection of photons off cat corpse; 8)experimenter's eye absorbs reflected photons; 9) more quantum interactions within the retina; 10)nerve impulse to visual cortex of the brain; 11)etc.; 12)etc, ... Eventually, the consciousness of the experimenter registers a result, at the end of a long chain of unobserved events.
The interaction between the experimenter and the experiment is actually no more mysterious than switching on a light in a dark room. The observer has altered the reality of the room by manipulating a contrived apparatus, not by peering intently into the gloom.
The conceit is in imagining that the mathematical formulations describing quantum events are complete and accurate, and therefore a "true" description of reality. That issue is far from being truly settled. The Semantic error arises out of that conceit, leading to imprecise and misleading common-language descriptions of events and interpretation of results.
For all its delusions of grandeur and primacy, solipsism is a symptom of a feeble sense of self, accepting itself as the author of all that is insane, chaotic, destructive and irrational in the world, as well as what little personal good and passing pleasures it can find. The ultimately petty mind of a solipsist would be incapable of conceiving and creating the tight-knit "conspiracy" of objectivist thought that opposes it.
Besides all that, if Solipsism were a valid thesis, people who were born blind could walk through walls.
And some close-minded idiot just came into the Link office to tell us that our Sexuality issue (which I helped produce) is "disgusting" and that we should "do better." The cover art is a painting my boyfriend did, of a woman contemplating a dildo. She isn't looking lasciviously at it or inserting it into any orifices, nor is her nudity titillating, as she is crouched on a bed and neither tits nor ass are visible. It's hardly offensive, but apparently masturbation is the greatest evil of all! Strange, since it's the sexual act least likely to harm anyone...
Stupid fucking prude hypocrites who can't even read the articles before they come in to judge us. It makes me so angry.