How can I know?

I’d say eftach that you can be experiencing real happiness, yet others can be even happier in at least a particular scenario. Or vice versa. Emotions are not static. The happiness one feels when one makes a $1000 is happiness, but it’s not the same as $10,000 or $100,000. Same with ruchniyus or for example simchas and life events (births).

I feel the root of the issue is not self esteem for you ;-), but the inability to appreciate the moment. Let me say that it is very normal. Any person who has something, will naturally ponder the possibility if they had more of that thing. L’mashal, they go into a delicious restaurant and get a great dish. Meanwhile, they see other great dishes. It’s only natural to wonder if theirs was as great as the others. One learns a blatt, and its great. But they note that there is so much to learn. Maybe they didn’t do what they should have? Maybe they didn’t accomplish or experience what was real learning?

Of course wanting to improve, wanting more good things is not bad. But by and large, a person needs to instill in themselves the greatness of the moment. One when is happy, let’em be happy. Let’em think of great state they are in. Let them thank Hashem for the kindness he has bestowed by doing something to make one happy. To analyze the potential that one’s happiness is insufficient is not not-normal but unhealthy.

nope, when you are happy you are experiencing what everyone-else’s neutral is, when you are sad that is others happy etc.

you have it all backwards, try re-routing your brainwaves.

How can I know the truth about anything? What I mean to say, is that if I am only me, and I only know my own experience in anything, then how can I know if it's normal or not?

You may well not be able to know. The color-blind sometimes go through much of their life not aware of the fact, and that is an issue which is easily testable.

Example: Many of us know people who are “not quite right,” but how many of those people are aware of it?

If you suspect others’ feelings or reactions are different from your own, perhaps you can ask them to describe them – if it sounds very different from your own experience, there may be a problem.

Eftach, my friend, if your experience does not include what you understand from others’ descriptions to be happiness, you may want to read up on depression – perhaps Dr. Twerski’s “Getting Up When You’re Down,” which I am fairly confident could not inspire you to misdiagnose yourself.

This question doesn’t bother you enough to interfere with living your life, does it?

It’s kind of like the sight thing. I call the sky blue. I have been taught since I was a child that the sky and things that are the same color are called “blue”. We’ve all been taught that. So you call the sky and similarly colored things blue as well. But maybe you’re really seeing what I know as yellow. Maybe our eyes interpret the colors differently but we’ve all been shown the same objects and taught their colors. But our colors could all be different.

But there is no way to know. You can only know what you’re seeing and what you’re feeling. And to compare wouldn’t work. Because we all define happiness based on how we’ve been taught happiness feels. So when you were an infant and someone gave you a cookie and said “Now aren’t you happy?”, you learned that whatever you were feeling then was happiness. And that it feels good. But that could be completely different from what I was feeling.

And this could go on forever. We can doubt everything we know and feel. But there’s nothing we can do about it.

1)

I think maybe we’ve focused too much on the “happiness” example.

Still, I’ll say this. Eftach, you can think about what you believe makes a person happy, and if you think you feel as good as you should in the situation you’re in (although the way you look at yourself and your situation makes a big difference in happiness, so take that into account). See also Yytz’s post.

2)

I also heard someone ask once that if something is there and no-one is there to see it, is it still there?

The answer science (and possibly Kabbalah) gives for that question might surprise you.

3)

Maybe our eyes interpret the colors differently but we've all been shown the same objects and taught their colors. But our colors could all be different. But there is no way to know. You can only know what you're seeing and what you're feeling.

Certainly an interesting concept, but I came up with a way to determine if this is occurring on a large scale.

Certain colors are known to have certain psychological effects – if we assume that our brains’ emotional responses to “objective” colors are uniform, then if enough of us were not seeing the same colors the same way, this could not have been an observable phenomenon. Rather, it would have been observed that not all people have the same emotional responses to color (though it is likely that such a phenomenon still exists between cultures that use various colors in different ways).

The concept is probably still useful in philosophical thought, though.

4)

Does anyone know the name of the concept that we never physically experience something, only our sensual perception of that thing?

(Unless perhaps during an out-of-body/near-death experience…)

Ah, existentialism.

“Does anyone know the name of the concept that we never physically experience something, only our sensual perception of that thing?”

Berkeley’s idealism.