Our various ordinary experiences are all similar in that they consist of various objects appearing to us. They are further similar in that if we investigate the nature of these objects with sufficient diligence, we will realize that the objects do not exist as solid entities, but actually arise from the coming together of various causes. They are further similar in that the objects that appear will withstand some limited modes of investigation. It is only when we look carefully enough that we will see the limitations.
It's like the Wizard of Oz. At first the great face and voice very definitely appeared, created fear, and inspired obedience. Later, upon further investigation, it became clear that the face and voice were merely appearing as the result of various circus tricks and there was no substance to the appearance. Ordinary experience, scientific experience, and dream experience are all similar in that they consist of various objects appearing that will withstand some investigation but not all investigation. These various types of experience differ in just what modes of investigation they can withstand and what modes reveal their limitations. That's why what we experience is called relative or conventional. In various situations we describe the world relative to some conventional modes of investigation. Oftentimes confusion arises when in a discussion two people are working with different conventions.
Experience has far more varieties than just the three of ordinary, scientific, and dream. These three themselves are just very coarse groupings. Consider rainbows. Do rainbows really exist? In some ways yes, in some ways no. Unlike dreams, many people can see the same rainbow at the same time. You can even take a photograph of a rainbow. One doesn't wake up from seeing a rainbow to the sound of the alarm clock buzzing, unless of course it was a dream rainbow! But if you try to grab a rainbow, you can never find anything to hold on to. Rainbows actually have no definite location; they have a direction, but no distance.
Lightning is another classical object of experience whose mode of existence can be contemplated. What is amazing about lightning is the contrast between the intense presence of its existence with its miniscule duration. By the time one can even formulate the idea of the existence of the flash of lightning, the lightning is already gone.
Consider the phenomenon of seeing stars when one is struck in the head. The stars most certainly do appear. Yet no one else in the room can see them, at least not right then. But others will likely have seen similar stars at other times, when they themselves had been struck in the head. Here is a curious variation on the theme of intersubjective experience!
"Did you watch the president give his speech last night?" If I watched a flickering image of the president projected on a phosphor screen by an scanning electron beam, I will still likely answer, "Yes!" What I saw and heard was not the actual president, but merely an illusion projected by electronic circuitry. Many other people saw the same or similar images. The next day I can talk with my coworkers about the phenomena that appeared, and we will all have had very similar experiences. Yet if I shout out a question or an objection or try to tweak the president's nose, I will certainly discover that there is no person actually present.
Some experiences we just stumble upon, other experiences we have to work to achieve. To watch TV, we might have to go out and buy a TV and then plug it in and turn in on and find a channel that works. Or maybe we have to get a cable hookup activated.
I am always amazed to reflect that of the three famous papers Einstein published in 1905, it was the paper on Brownian motion that won him the Nobel prize. (The other papers were on the photoelectric effect and on special relativity.) Still in 1905 it was controversial as to whether or not atoms and molecules actually existed or were just a convenient fiction for explaining the regularities of chemical combinations. Einstein used Brownian motion to measure the size of molecules, thus settling the controversy in favor of their actual existence. Nowadays we have scanning tunneling electron microscopes that can generate clear images of arrangements of individual atoms! We generally take the existence of atoms for granted, but it took the work of many genius scientists to build up the equipment required to make atoms clearly appear as existing objects. Geiger and Rutherford exposed the internal structure of the atom, revealing electrons and nuclei and the vast empty spaces that constitute atoms. The history of microphysics in the twentieth century is a continuing sequence of ever new modes of investigation revealing the limited nature of the existence of one class of objects by making apparent how those objects are built up from arrangements and interactions of yet finer objects.
Each scientific discipline has its own conventional methods of investigation and its own objects that appear through the application of those methods. What appears for a zoologist to be a horse looks for a chemist to be a system of interlocked chemical reaction processes and for a physicist to be a configuration of particles coursing along trajectories determined by fundemental force field equations. An economist might see an investment with certain anticipated risk and return!
If we investigate a phenomenon closely enough, then we will discover that the objects that appeared are really just limited rough approximations to the real facts, facts that incorporate a whole range of deeper phenomena that came into focus as the investigation unfolded and that together explained how the phenomenon came into appearance. Yet at the same time that we can understand and reflect upon the limited nature of the existence of whatever objects might appear to us, still when phenomena appear, they do truly appear. In one sense a rainbow does not really exist but is merely an appearance generated by light and mist. In another sense, a rainbow most certainly exists as a circular pattern of brightly colored stripes. All phenomena have this twofold nature. Ultimately one can always investigate deeply enough to reveal what is behind an appearance and the limitations of that appearance. But apart from those investigations and within those limitations, phenomena do arise and appear.