Reality is comprised of many things -- from light, to sound, to molecules, from the stars in the universe, to the sand on the beach, to the trees in a forest, from the people in the city, to the objects in your living room, to the organs in your body. How to think about reality? Think about it.
A red apple is an object that is made of atoms which consist mostly of empty space and that reflects light with a wavelength of 700 nanometres.
We have an external reality that is translated into an observation which is then translated into a statement about the observation.
The first translation, between external reality and observation, falls into a branch of Psychology called Sensation and Perception. For an observation to happen three transitions must occur: First, in a process called transduction, your sense organs convert the external input from your physical environment (electromagnetic waves, pressure waves, molecules) into neural activity. Second, in a process called sensation, your brain extracts relevant information from the neural activity resulting in vision, hearing, touch, smell, and taste. And third, in a process called perception, your mind interprets these sensations in a meaningful way, e.g. the colour red of an apple-shaped apple-tasting object. The details of sensation and perception are complicated and not fully understood.
The second translation, between observation and a statement about the observation, involves an abstraction. This abstraction may be spoken language (somebody saying /hɔː(r)s/), written language (the word "horse"), pictorial (a drawing of a horse), numerical (Number of horses in my living room = 0), mathematical (an equation describing the number of horses in my living room as a function of time), or graphic (a graph showing the number of horses in my living room as a function of time).
Often, we can measure external reality using scientific instruments that translate measurements of things we cannot observe (wavelengths, radioactivity, bacteria on a surface) into something we can observe (colours, sound, numbers).
All of this would be difficult enough if external reality were static. But external reality is not static, it is dynamic, things change, light turns into heat, atoms form chemical bonds, molecules disintegrate, calves are born, cities grow, mountains erode.
The whole of external reality at a particular point in time may be thought of as the system state S at time t (the number of trees in a forest, the number of fish in the ocean, the number of infected animals in an epidemic). The system state S at time t changes through natural processes, i.e. flows of matter and energy that follow "natural laws" (Figure 1).
Human actions are a consequence of human choice that is based on the information state. The information state changes through cognitive processes, i.e. removal of information and perception of new observations of a previous system state. The quantity and the quality of new observations is influenced by the previous information state.
Figure 1: The physical sphere (black) and the cognitive sphere (grey): Black rectangles represent system states S at times t-1, t, and t+1. respectively. Solid lines represent flows of matter or energy. The system state is the vector of all state variables. Grey rectangles represent information states I at times t-1, t, and t+1. respectively. Dashed lines represent information flows. The information state is the vector of all information, knowledge, and understanding, as held by an individual, a government, a society, or all of humanity. Note that I includes human values, objectives, and utility functions.
Looking at the processes depicted in Figure 1, one could conclude: Mother Nature hates us.
1: She limits our access to information, resulting in incomplete and/or inconsistent new observations of any given phenomenon, resulting in incomplete and/or inconsistent information states.
2: She bars us from observing causes directly. Rather we must infer causes by comparing consecutive information states. These information states may suggest non-unique causes (i.e. different system states at time t result in the same system state at time t+1) or non-unique effects (i.e. the same system state at time t results in the different system states at time t+1).
3: She never varies only one variable at a time, which makes it difficult to assign a cause for an effect.
Observing the world, extracting information from it, and acting on this information is not a trivial matter.