NOTE: Lately I have been contemplating what it means to “know” something as true or false. What follows is the beginning of my attempt to explore this, and similar questions. My thoughts on the subject are highly influenced by David Hume.
All human knowledge is a direct function of human experience. Human experience comes in two separate, but related, forms. The first form is the experience of the five senses: taste, smell, touch, sight, and sound. The second form is experiences internal to the human mind: emotion, general thought, idea formulation, etc… Of course, the internal workings of human experience are essential to interpret and contextualize the experience of the external senses and so, in some sense, all human experience, or at least the interpretation thereof, can be classified as internal to the human mind.
Similarly, human experience can be classified as either demonstrable, or non-demonstrable. Demonstrable experience is that experience which can be shared with others through means of their external sensory abilities. For example, if I have learned from experience that gasoline burns when it comes in contact with fire, I can easily demonstrate this to others by throwing a lighted match into a canister of gasoline. Through their external senses, they will see the cause, the match, and the effect, fire and/or explosion. However, imagine that I attempt to demonstrate this cause and effect relationship with a person who is blind. His/her experience upon my demonstration will differ in key respects to my own. Thus, their experience may be interpreted internally with greater weight or importance being given to the smell of the fire, or the sound of explosion. So, while we may have both been party the same demonstrable event, our experiences differ. So at best, our experiences can be demonstrable to others but it is impossible to know that their experience of that event will be identical to our own.
Non-demonstrable experiences include those internal experiences that are emotional, spiritual etc… Such internal experiences can be expressed to others through language but cannot be otherwise illustrated. For example, I can describe the love I have for a family member or the my experience in tasting a fine wine, but at best, my description of such experiences can create a cerebral understanding or appreciation within others, but the experience itself cannot be duplicated.
Yet, even for me to express the ideas of love, emotion, taste, smell, etc…. I must share a common context with the person to whom the idea is to be conveyed. We must speak the same language and, within that language, must have a shared understanding or agreement on terms. This is especially true when seeking a consensus on the meaning of shared experience. For example, scientists measuring the temperature or length of an object must do so by employing the same system. Otherwise, the statement of temperature of measurement has to implicit meaning. Its implications, and any inference drawn from the measurement, derive from the consensus created by a shared system and language.