Many people derive comfort from the idea that there is an objective reality, and that there are objective truths, independent of our own individual subjective perceptions. Why should this be so? Why isn't the pursuit of hedonism enough for some people?
We can feel comforted by the existence of truths which are not merely subjective because the alternative that there are none is quite uncomfortable. Were there no truths, and nothing other than subjective perceptions, we should find ourselves with at least these two very uncomfortable thoughts:
If when we are harmed by someone else, there were no facts of the matter about what happened, there could be no hope that judges and juries could approach an accurate understanding of what happened. Our understandings of situations are always limited by our perspectives and our limited information, but we can often acquire some further understanding about those limitations themselves. We can acquire knowledge of the ways in which and degrees to which our knowledge is limited. If there are no facts, then it is not coherent to say we are epistemically limited in this way. Rather, each of our subjective impressions is as good as any other. So if a crazy person says I stole his money, that claim is on equal epistemic footing as my claim that I clearly did not. Without the ability to describe claims as better-grounded or worse-grounded, our ability to resolve situations justly, situations where we are harmed or accused, is fundamentally undermined.
Without the sense that we can trust that aspects of the world are stable to some degree, and can be known to some degree in more objective ways, it would be quite scary doing ordinary activities like walking and driving. It would be paralyzing to think that I can't know at all whether the sidewalk on which I'm about to step is going to be solid or liquid or gel or plasma. If it's a merely subjective matter, I have no ways of assessing that I'm probably right that the sidewalk is solid. Similarly, it would be uncomfortable not to be able to trust that there are facts that the engineers of cars and bridges and tunnels have more access to than does a child or a person using LSD. That is, it's frightening to imagine that neither I nor they have beliefs that approach any facts.
Objectivists do not merely "derive comfort" from the idea of an objective reality, it speaks to the very core of what Objectivism is. It is a pillar upon which all of Objectivism is based.
Consider the question, "Why do Christians derive comfort from belief in God?" The question is almost nonsensical because most of the actual comfort is derived from a chain of reasoning/conclusions based on this presupposition.
- It is what makes everything else Objectivists believe possible.
Similarly, if you study what Objectivism considers "axiomatic concepts" (irreducible truths, or "A truth you cannot prove nor do without" ), 2/3 are directly related to an objective reality.
- Existence exists
- The Law of Non-Contradiction (law of identity, A=A, etc...)
Hedonism by contrast doesn't present any in depth conception of reality (metaphysics), or any theory of knowledge (epistemology), but attempts to skip over all of the tedious "leg work" and move straight on to Ethics. The scope of hedonism is very narrow in relation to Objectivism, and isn't really even a legitimate alternative.
If I can contribute to the conversation, I would like to think that objectivity is an essential feature of social animals or species who rely on one another for survival. Haha, it is kind of darwinian, but imagine if we didn't agree on set standards, rules, laws, codes, etc. It makes the act of coordination very difficult especially when we have to coordinate such a complicated society like the one we live in now. I wonder if objectivity is more or less crucial to species with less advanced communication/coordination abilities?
I will add that without any possibility of objectivity, that would mean the universe in a state of constant flux, where opposites are both true at the same time, and there is no truth of any matter, as it's all subjective, where nothing exists independently of the human mind in any concrete and unchanging way. Heraclitus, in Ancient Greece, was one of the first philosophers to expound these types of ideas in Western philosophy; however, the notion of non-duality, where there is no divide between object and subject predates the Greeks. Arguing for an external reality that exists in the way it is, regardless of how we perceive or think it is, is crucial coherent thought. The empirical world, which is what we perceive with our senses, may be unknowable to us, but what we should not deny is the notion of coherence itself and that there is an external world existing independently of our ideas or notions of it — it just is. Objectively, no matter who the philosopher is, the law of identity, where A = A, should always be true. What is, is, What is not, is not. At the very least we would be justified in claiming that our knowledge of reality is approximated by scientific understanding and sense perception. Whether this understanding is ultimately true isn't knowable with absolute certainty, although absolute certainty is not needed to understand our physical reality around us. If our senses are failing us, we can't know what the alternative would be, as this is an impossibility: To know what something is like when we are not using our senses to perceive it, which is known as a transcendental realm, and independent of experience.
To your last question:
Why isn't the pursuit of hedonism enough for some people?
Because hedonism, in the usual sense, where we think about revelry and sensual simulations, doesn't aid the process of attempting to discover knowledge or truths where we can know them, as it can completely distract from this end, and heavily distort cogent thought formation, unless you would count the pursuit of knowledge as a pleasurable activity in itself, which I do.