Aesthetics- The branch of philosophy that deals with the nature of art, beauty, and taste, with the creation and appreciation of beauty
Epistemology- The branch of philosophy that is concerned with the nature and scope (and limitations) of knowledge.
Ethics- The branch of philosophy that deals with ethical debates (right and wrong, good and bad) and decisions (includes religion).
Logic- The branch of philosophy devoted to examining the scope of nature and logic.
Metaphysics- The branch of philosophy concerned with explaining the ultimate nature of reality, being, and the world.
Political Philosophy- The branch of philosophy that is devoted to the study of political systems.
Religious Philosophy- The branch of philosophy devoted to the study of religion.
Social philosophy- The branch of philosophy that is concerned with the study of questions about social behavior
Basic “isms” Defined
Despite the large number of philosophical schools and subtle nuances between many, all philosophies are said to fall into one of two primary categories, which are defined in contrast to each other: Idealism vs. Materialism.
Despite the large number of philosophical schools of thought and subtle nuances between many, philosophy can be divided into two major directions of thought, centered on what is considered to be the two fundamental questions in philosophy:
What does reality consist of? (Metaphysics) 2) Where does it originate? (Epistemology)
Idealism- The belief that the mind and ideas is the primary structure of reality and that physical or material reality is secondary. (Plato)
Materialism- The opposite of Idealism and sees matter as the primary reality and all other things including thoughts as the product of interactions of matter.
Rationalism- The belief that the rational mind is the best way to know something. If you are a rationalist, you believe that your mind is more trustworthy than your sense. A stick in the water might look bent, but you know rationally that it only looks that way because it is in the water.
Empiricism- The opposite of rationalism and it is the belief that the senses are the best way to know something. You might think something is true, but you only know it is true if your senses confirm it.
In consideration of the above, it is good to keep in mind that you can’t be an Idealist and a Materialist, and you can’t be a Rationalist and an Empiricist. On the other hand, you can be an Idealist and a Rationalist or an Idealist and an Empiricist. You can also be a Materialist and a Rationalist, or you can be a Materialist and an Empiricist.
That is because Idealism and Materialism are statements of metaphysics, which means they are statements about what you believe is real. Rationalism and Empiricism are statements of epistemology, which means statements about what is the best way to know what is real.
The "Inside-Out" Tradition
In the history of Metaphysics, there are two quite distinct traditions about the nature of the relationship between our self and the world we see around us - between what we think we perceive and what believe is real; and centrally, between the meaning of "perceive" and the meaning of "real". They are the Idealist, or the "Inside-Out" tradition and the Materialist or "Outside-In" tradition. The difference between the two traditions is the difference in their approach. The Outside-In tradition sets out what must in a very general way be the case about the world and about ourselves if the world exists independent of our consciousness of it. The Inside-Out tradition holds that only things answering to certain criteria are real with the result that there are distinct realms to be called "appearance" and "reality" respectively.
Philosophers of the Inside-Out tradition maintain that our modes of consciousness and cognition constitute, modify, or process what we perceive as sensory inputs. What our consciousness is aware of as sensory evidence must be regarded as the products of our consciousness rather than unbiased evidence of reality. In that event, goes the inescapable logical conclusion, either we can know nothing about the "True" nature of an alleged external reality, or anything that we can know about such an alleged external reality must be provided through other means than our senses. The proponents of the "Inside-Out" line of reasoning assume that consciousness, as prior and primary to the sensory evidence, must generate our understanding from the evidence provided by our processes of perception. Perception is a separate process from our conscious awareness of what we perceive. Our understanding of what we perceive is not a pure product of our senses. Therefore, what we understand about our perceptions cannot be trusted as evidence for a separate reality. We have no independent basis from which to validate the evidence provided by our senses. All we have is the evidence of our perceptions. And our perceptions are highly processed information from our senses.
There is, therefore, no logically valid line of reasoning that can proceed from the basic axiom that consciousness is the fundamental given, to the conclusion that there is a reality outside of, or separate from one's own consciousness. Since there is no way to validate the evidence of the senses (the senses being the only source of information), there is no basis from which to conclude that the sensory evidence is valid evidence of an external reality. There is no way to distinguish between "reality" and a dream or hallucination. Philosophers of the Inside-Out Tradition therefore almost universally conclude that all that is perceived (ie. all the evidence), as well as all the contents of consciousness, is actively a product of consciousness. As it is impossible to logically derive the existence of a reality beyond our subjective experience, therefore there can be no knowledge of such an external objective reality. Hence, there is no acceptable proof that there is such an external objective reality.
The inescapable consequence of this conclusion is that there can be no possible logical foundation for any constraints on the nature of the contents of a particular person's consciousness. There can be no logical foundation for any standardization or similarity of the contents of consciousness from one person to another. For this reason, the Inside-Out tradition logically results in what is referred to as "Subjectivist" (or sometimes "Anti-Realist" ) notions of Truth, Knowledge, and Ethics. And, ultimately, to metaphysical "Solipsism".
Idealism (“Inside-Out”) vs. Materialism (“Outside-In”)
Let us consider some very basic features of our being. We sit, for instance, on a chair. We can see the chair, we can touch it, and the other senses can, as well, perceive of the chair. Now, these perceptions all occur within our brain, where the input data of the sensory organs come together and form an "image" of the thing we perceive (the chair in this case).
A central issue in this is whether or not we regard the thing (the chair) that caused the perceptions (sensory experiences) as real or not. Is there really a chair that we are sitting on? Does the chair really “exist” outside of our minds?
Materialism answers the chair question with a clear: YES- THERE IS A CHAIR. Not only by our senses but also through science and instruments, we can know about this object that is separate from our mind. There is an objective world, independent of our mind. The objective world consists of what is called matter, which has the property of being in motion (undergoing change) at all time. Space and time just denote the modes of existence of matter. The theory of materialism holds that the only thing that exists is matter or energy, that all things are composed of material and all phenomena (including consciousness) are the result of material interactions. In other words, matter is the only substance, and reality is defined by the occurring states of energy and matter.
According to the Catholic Encyclopedia, materialism denies the existence of both deities and "souls." It is, therefore, incompatible with most world religions including Christianity, Judaism, and Islam. In most of Hinduism, all matter is believed to be an illusion called Maya, blinding us from knowing the truth. Maya is the limited, purely physical and mental reality in which our everyday consciousness has become entangled. Maya gets destroyed for a person when they perceive Brahman with transcendental knowledge. In contrast, Joseph Smith, the founder of the Latter Day Saint Movement, claimed, "There is no such thing as immaterial matter. All spirit is matter, but it is more fine or pure, and can only be discerned by purer eyes; we cannot see it; but when our bodies are purified we shall see that it is all matter. This spirit element has always existed; it is co-eternal with God. It is also called intelligence or the light of truth, which like all observable matter was not created or made, neither indeed can be." (Teachings, pp. 352–354.)
Idealism answers the chair question with a clear: NO- WE CANNOT KNOW IF THERE REALLY IS A CHAIR. To idealists, spirit or mind or the objects of mind (ideas) are primary, and matter secondary. To materialists, matter is primary, and mind or spirit or ideas are secondary, the product of matter acting upon matter. Apart from our immediate perceptions and awareness of the world, there is no such thing as an outside, objective world since our perceptions are based upon our senses, which can be flawed. The world takes place entirely within our mind. Outside of that, nothing exists. Idealism asserts that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Idealism, thus, rejects materialist philosophies because they fail to ascribe priority to the mind.
Thus Kant defines idealism as "the assertion that we can never be certain whether all of our putative outer experience is not mere imagining". He claimed that, according to idealism, "the reality of external objects does not admit of strict proof. On the contrary, however, the reality of the object of our internal sense (of myself and state) is clear immediately through consciousness."
So, these opposing philosophies contradict each other in their definition of what the world is consisting of in primary instance. Materialism claims that in first instance the world is just matter in motion. Our mind, brain, and body only denote a specific form of matter. So, our mind, awareness and thoughts, are a secondary property of matter.
Idealism, on the other hand, claims that there is no such material world, and that the world in first instance is our mental process, our mind and thoughts. That what is perceived, and which behaves ordinary, is not an entity in itself, but was created in or by the mind.
Where does Solipsism fit in?
Solipsism comes from the Latin "Solus ipse" - the sole self. Anthony Flew defines solipsism as "The theory that I am the sole existent. To be a solipsist I must hold that I alone exist independently, and that what I ordinarily call the outside world exists only as an object or content of my consciousness."(1) Thomas Mautner defines it as "(1-metaphysics) the view that nothing exists except one's own self and the contents of its consciousness; (2-epistemology) the view that nothing can be known except one's own self and the contents of its consciousness."(2)
Clearly "in here" is distinct from "out there". In here, I am me. Out there is everything else that is not me. The distinction is self-evident. Solipsism is the belief that one's self is the only thing that exists. It is the extreme form of Idealism about our evidence of reality. Solipsism is the doctrine that, in practice as well as principle, "evidence" means for me my experiences, "reality" means for me the world that I perceive, and "existence" means for me my existence. In other words, everything which I experience - everything that is not-me (other people, events and processes, in short anything which would commonly be regarded as a constituent of the spatio-temporal matrix in which I exist) - just part of the content of my experiences, of my consciousness. Other objects, including other beings that may appear to exist separately from me, are actually just projections of my own consciousness upon my experiences. According to Solipsism, I see the world through the eyes of my mind. The world is only as I perceive it. Reality is only that which seems real to me. Knowledge is what I know. Egoism is the only possible ethic - my welfare the only possible concern.
Solipsism is sometimes expressed as the view that “I am the only mind which exists,” or “My mental states are the only mental states.” However, the sole survivor of a nuclear holocaust might truly come to believe in either of these propositions without thereby being a solipsist. Solipsism is, therefore, more properly regarded as the doctrine that, in principle, “existence” means for me my existence and that of my mental states. Existence is everything that I experience — physical objects, other people, events and processes — anything that would commonly be regarded as a constituent of the space and time in which I coexist with others and is necessarily construed by me as part of the content of my consciousness. For the solipsist, it is not merely the case that he believes that his thoughts, experiences, and emotions are, as a matter of contingent fact, the only thoughts, experiences, and emotions. Rather, the solipsist can attach no meaning to the supposition that there could be thoughts, experiences, and emotions other than his own. In short, the true solipsist understands the word “pain,” for example, to mean “my pain.” He cannot accordingly conceive how this word is to be applied in any sense other than this exclusively egocentric one.
The interesting feature of Solipsism is that there is no discernible difference between the Solipsist's experiences of the world, and the non-Solipsist's experiences of the world. In both cases their respective experiences will be rich, complex, and varied. Further, there is no fundamental reason for a difference in moral attitude between the Solipsist and the non-Solipsist. The only difference is their respective metaphysical assumptions about the ultimate foundation of those sensory experiences. The Solipsist maintains that there is only my experiences. The non-Solipsist maintains that there is something extra beyond my experiences. But the Solipsist can draw upon Ockham's Razor to argue that there is no discernible benefit to me, and no discernible difference to my current or future experiences, from positing anything in addition to the summation of my personal experiences. Not only can the existence of an external reality not be proved, it is not even necessary to adequately explain all of my past, present, and future experiences.
The challenge that Solipsism raises for the study of philosophy is that while it seems to be a logically sound theory of existence, no one likes the implication that they are completely alone in the Universe. It is also universally (and frequently offensively) rejected by philosophers as an acceptable basis of metaphysics. Yet given certain popular metaphysical premises, philosophers have difficulty in rationally supporting this rejection. Hence the challenge that Solipsism presents.
The Problem of Solipsism
Solipsism is a huge problem for anyone interested in promoting introspection as a way to understand the mind. You can only introspect on your own mind, not anybody else’s. So technically, all you really know for sure is your own mind. The existence of any other minds is purely hypothetical.
The same would go for the existence of the entire world. If you accept introspectively known sense impressions as valid information, you realize that you have no other information. All your sensory data are known to you and only you, by mental impressions. A touch on the arm is known as the mental feeling of a touch on the arm. The arm itself knows nothing. All you can know for sure is the mental impressions you have of the world. You can’t know if anything else is really “out there.”
In the most extreme form, a Solipsist asserts, “I am the only self that exists. All the rest of the world is, at best, a hypothesis, or possibly just a figment of my imagination.”
There is no way to refute Solipsism. Any counter-argument against it would just be another figment of my imagination. If it is false, I could never know it, because my own mind is the only thing known to me. Solipsism is an extreme form of idealism, which says that only mental events can be known to exist (or, only mental events do exist).
True Solipsism would require that I do not experience myself as a single self in distinction from other selves, but that I experience myself as the only self that exists. But that is impossible, for self is only defined by other. So again, Solipsism is impossible in principle.
Remember, all this started with the fundamental premise of the Inside-Out Tradition that consciousness is primary, that the mind is something separate from an objective reality, that we have a direct knowledge only of our minds and its contents and not of the source of our sensory perceptions, that there is a dichotomy between "reality" and "appearance". This was combined with the Empiricist premise that all human knowledge derives from our sensory experiences. So, if you don't like Solipsism as a metaphysical theory of what actually exists, adopt alternative premises. Either, like Aristotle and other "realists", the premise of the Outside-In Tradition that existence is primary, that the mind is a product of the prior existence of reality, that we have as direct an access to the source of our sensory perceptions as we do to the contents of our mind, that there is no dichotomy between "reality" and "appearance". Or, like Descartes and Kant, the Intuitionist premise that the mind has access to sources of knowledge other than our sensory experiences - innate pre-programmed ideas and concepts, or an ability to "intuit" a priori knowledge without the contribution of the senses . Or, like Descartes and Berkeley, the Theistic premise that there is a benevolent God to bridge the gap between my mind and the "other", that we can gain from "divine revelation" knowledge not available to our senses.
In other words, if you don't want to be a Solipsist (the logical consequence of Empirical Idealism), you have to be either a Realist (of the Outside-In Tradition), or a Rationalist (Intuitional Idealism). No professional philosopher will admit to being a Solipsist. They have all sorted themselves into one of these two alternative groups. So no matter which alternative you choose, you will have the company of lots of professional philosophers. Solipsism is logically coherent in itself, but we are incapable of believing it, once the consequences of the theory are made plain. And "believability" is the ultimate criterion of the truth of metaphysical theories.