“Reality” is defined as the existence and the behavior of everything in the universe. Sometimes we call it “Nature”. In ancient India religion, Sanskrit called “Dhrama”, Pali called “Dhamma”. In ancient China called “Tao” or “Dao”.

Once human beings exist in the universe (at somewhere in this world), they can touch the universe (their environment) through their 5 sensors. The feeling of touching is called the “Knowledge”.

Knowledge is the model of reality created by our “Soul”. In Buddhism, soul is called “Knowledge Element”. Reality and knowledge are not the same thing. For example, a ray of electromagnetic wave of frequency 400-790 Tera Hz. reach our eyes, our soul will map it to red color. We don’t know what reality is, we only know that we see red color. Tao said, “What we see may not be realism.”

When our sensors detect signals from nature, “Emotions” are added to our feeling before send to our “Spirit” for making decision or response. Soul creates emotion to spirit as a direction of life. Smiling faces, nice looking girls, or handsome boys, make our spirit want to get approach. Ugly things and scarry places make our spirit to get away. Laughing noise makes us happy while screaming noise makes us scared. Beautiful music, good smell, delicious food, and sex make us feel like being in heaven while bad smell, bitter food, pain, and heat make us fill like being in hell. Emotions specify the direction of life is to choose heaven and avoid hell.

Human’s spirit has 4 duties as follows:

1. Receive senses and emotion created by soul.

2. Think (analyze the information) and imagine.

3. Control our body.

4. Memorize (record knowledge such as sense, emotion, event, and imagination in our memory).

Feelings from our 5 sensors (eyes, ears, noses, tongue, and skin) always come together and also repeat the same set. A flame of fire is always red and hot. Water is always soft and cold. Black Coffee always has a good smell, and the taste is bitter. Man voice has low tone while women voice has sharp tone. Everything we can feel is named and the set of feelings are called its properties. These knowledges are recorded in our brain as models of realities and being our normal “experience”.

Naming things, properties, and their behaviors come together with the development of language. Everything is named, even the emptiness. Speaking language is another kind of model used to mapping reality with sound of human voices. Speaking language is limited with our memory to remember while written languages (another kind of mapping reality with letters) could be unlimited to record the knowledge of our universe. The time period since Human Being started recording until now is called “Historic Era” while the time period before that is called "Prehistoric Era”.

The behaviors or events in our universe also happened repeatedly. Sun raises in the East and sun sets in the West every day. We found the life cycle of plants and animals related to the seasons. When objects or events in reality are hidden or invisible, our spirit could interpolate the missing models in our mind called “Imagination”. Magicians try to play with our imagination. Imagination does not only create the models of events or objects in hidden location but also predict the “Future”.

Imaginary models of the same thing vary between persons, but we believe that there should be only one true model to represent reality. Once reality is revealed or the time is reached and when our sensors detecting reality is the same as our imaginary model, the model has been proved. This kind of truth is called “Apparent Truth”.

There are other methods to prove the imaginary model by using reasoning called “Logic”. Logic is the procedure to find new truths from the known truths. This kind of truth is called “Logical Truth”. Geometry and Mathematics also give us logical truth. Budha’s enlightenments are logical truths.

Imagination is a powerful tool to get knowledge. Once we create an imaginary model in our mind to answer some questions, this model is called “Hypothesis”. After hypothesis is logically proved, it becomes “Theory”. After theory has been apparently proved, it becomes “Law”. Imagination is the starting point to find knowledge. Albert Eistein said that “Imagination is more important than knowledge”.

When humans are sleeping and dreaming, all sensors stop working. We would not hear even our snoring sound. During dreaming, some part of their spirit is still working. Most people see black & white pictures, but some could see color pictures. In the dream, our body has no weight. Distance in the dream is meaningless. Dreaming is out of our control. We do not know what night we are going to dream and what situation we would encounter during dreaming. Someone also believes that dreams are a signal of future events.

During dreaming we believe that what happens at that moment is real. And after waking up, we believe that our real world is real. If somebody could control all our sensors, we would not know what is real and unreal as the movie “The Matrix”.

Most of our knowledge is from other people’s experiences through languages. We could not apparently prove all our knowledge, and we fully believe only appear to our sense to be true. The level of belief from others will be lower depending on the source of the knowledge.

Scientist has set up the proving method for proofing their knowledge as follow:

1. More than one person feels the same thing (apparently prove).

2. The experiment can be repeated and get the same result.

Scientific theories have been proved by the above method would be changed if new experiments are performed. Like we use our hand to touch something in the black box, the more times we touch keeps changing the model of that thing in our mind. The more experiments keep changing the scientific theory. Changing to be better means the growth of civilization, while unchanged would be disrupted.