It is only through our own experience that we can come to know anything, and the world we live in is the world of our personal experience. It makes sense, then to look at the fundamental elements of which our experience is composed, its furniture, if you will.

Experience consists of only three types of things: 

Concepts: Ideas, things we can think
Facts: Things we can know
Phenomena:  Things that we can perceive

Concepts include things like the concept of a horse, or the concept that fulfillment in life depends on hard work, the concept of roundness, or the idea that it is important for children to be required to do chores.

Facts are concepts to which one has given one’s assent. Without this additional element, a concept remains just an idea. In the case of a quality like roundness or “horseness”, giving one’s assent means that these concepts are instantiated, i.e., that some things are round, or that at least one horse exists. The concept of a unicorn is, for most people, not assented to, so unicorns are not considered real or factual. A proposition is just a concept unless it is assented to.  Take the proposition, “The cat is on the mat.”  One can have the idea of the cat being on the mat, but unless one gives one’s assent to this proposition, it’s just an idea, not a fact.

How can we get a handle on these often elusive elements of experience? In speaking of facts and concepts, Plato used the metaphor of birds in an aviary.  At any given time, some are more accessible than others. Humans do not have an unlimited ability to bring ideas to mind or to keep track of all the facts they know. In order to make these more accessible and manageable, humans have invented language. Language, particularly written language, is a handy way of keeping track of our ideas for later reference and communicating them to others.  The meaning of a word, phrase, or sentence is the concept it invokes in oneself or others.  When you want to share a concept, you put it into words, and if the sharing is successful, the other person experiences the concept you are trying to share. If a fact exists for you in your world, you use words to present the underlying concept to another person and then you can invite them to assent to it.

Phenomena include things like houses, chairs, as well as physical and emotional feelings and what are referred to as sensations, although raw, unprocessed sensations cannot be experienced, as a certain amount of factual content (i.e. knowledge) is always present. Even newborns do not live in a world of raw experience. They have a built-in “starter kit” of knowledge that tells them when things are close or far away, that enables them to perceive the edges of things, differentiate light from dark, recognize faces as being different from other things in the environment. As a person learns, more and more knowledge gets embedded in perceptions, so now, for instance, one can learn to identity types of objects, such as chairs. One does not experience a mass of pixels of experience; one perceives a chair.  With further training, we see the world in more and more sophisticated ways.  A lay person looking at an x-ray sees only bones and vague shadows, while a trained radiologist will see actual organs and their state of health.

Since all that we know is literally contained in our experience, it is not possible to use correspondence with a reality outside our experience as a criterion of truth. As Kant pointed out long ago, that is an impossible task.  How, then, do we decide what is true or real? This can also be expressed as “How do we decide what to say “yes” to?” Borrowing a term from biology and using it in a philosophical manner, I call this the process of ontogenesis. Starting from the elements of experience that we know are real, that have a sound ontological status, we build on this foundation to discover other things that are real. In other words, over time, we rearrange the furniture of experience in the best way we can. That applies to the literal furniture we have around us, but also to our other experiential furniture, as we add to and arrange the facts in our worlds.  We do not do this randomly or arbitrarily, but follow certain ontogenetic criteria, many of which are hardwired in human beings, such as the rules of logic: inductive, deductive, and adductive as well as principles like Occam’s Razor that help us to create as simple and self-consistent a belief system as possible. We also try to construe and construct our world of experience in such a way that we can maximally understand and control it.  In dealing with our world, it is as though we are doing the best we can to create a pleasant and user-friendly user interface.

Since people, in general, use the same basic criteria in deciding what to agree to, it is often possible to get agreement from another person by sharing the reasoning process one used to arrive at assenting to a certain concept and by referring to phenomena that can be shared. The basic laws of science and mathematics can usually be agreed upon in this way, through evidence and reasoning, although as Karl Popper explained, these can undergo major paradigmatic shifts over time.  This brings about the concept of an “external world” in which we all live, but it is better thought of as a shared world. Other more emotionally charged or culturally based concepts are generally agreed to by only a limited number of people. These do constitute the real world for those people, however.

In building our reality, we cannot rely entirely on our own reasoning and perceptions but often must go beyond our personal experience and rely on others as an authoritative source of information. Parents, of course, are the first authorities we rely on. Later, we learn to apply empirical principles to decide which authorities to believe.  Has this authority proven correct in the past? Are the ideas of the authority self-consistent? Does the authority always say what is true for them, or do they sometimes lie? Is what the authority is saying consistent with what we already know? If not, can the authority lead us in a chain of reasoning that allows us to change or add to our view of reality?

In soliciting your agreement with what I am saying, here, I urge you to consult your own experience and decide whether the furniture of experience I have described above is true for you.