Your point is valid, but I think it's much weaker and less widely applicable than you claim.
In many cases, people know definitely that they will not solve a certain problem; I think this applies to many people and problems, and is one of this post's main targets. Perhaps they definitely cannot affect it, like I can't stop the prison torture. Or perhaps they have consciously decided not to try to solve it, and invest their effort elsewhere. However, emotionally, being aware of the problem often causes suffering. This suffering is needless and it does not help to solve the problem, or any other problem that these people are trying to solve.
In addition to e.g. sadness, there are other emotions. One example is fear, which led to this post. The person there was afraid of failing at important future tasks, or of bad things happening beyond their control. Empirically, more than a small amount of fear does not server to further motivate us to prevent such problems. On the contrary, it sometimes paralyzes and prevents action. We should therefore strive to minimize the amount of fear experienced to be at least no greater than needed to motivate us to act.
Negative emotions can induce bias such as looking away from problems. In the absence of bad emotions, we can deal with problems more rationally.
Once we have decided to solve a problem, the original emotion that made us decide this has become less necessary. We can consciously, rationally, sustain our fight against the problem even in the absence of the emotion. This is analogous to pain which continues after a wound has been treated, and is counterproductive. This is an argument for reducing the amount of negative emotion we allow ourselves to feel.
Happiness isn't sadness with a negative sign. Reducing the amount of sadness isn't the same as increasing the amount of happiness. Both sadness (because there is a problem) and happiness (imagining the potential solution) can motivate us to solve a problem. If we increase positive motivation at the expense of negative motivation, this is a good thing.
Do you really believe that someone who felt happy despite knowing about the state of suffering in the world would be more strongly motivated to reduce suffering than someone who felt a great sadness and a burning emotional desire to stop it every time they thought about it?
Not necessarily - though it is possible (sadness can be paralyzing, depressing, and disruptive). But at the very least I do believe the happy person should not be significantly less motivated than the sad person - if they remember being sad, and preserve the (a-emotional) decision to solve the problem.
Do you think being happily mortal is the best emotional state for crusading to stop death?
I don't propose being happy about being mortal. I do propose being less sad about being mortal. Being "sadly mortal" in the sense of constantly being sad is demotivating and I believe counterproductive. Enjoying life is a mentally healthy state and is conductive to work, including work on immortality tech.
See, I feel the same way about your post as you do about my reply. I think that you're getting at something, but you've significantly overstated your argument -- to the point that someone following its recommendations would be less effective.
(There's something bizarrely wrong with the autoformatting which I can't reproduce and can't fix -- 1, 2, and 3 all address part 1, 4 is 2, and so on.)
a. ("perhaps they definitely cannot affect it") This is true if you can do literally nothing about it, but the number of things on which you can have literal
Related to: I'm Scared; Purchase utilons and fuzzies separately
Expanded from this comment.
You have awakened as a rationalist, discarded your false beliefs, and updated on new evidence. You understand the dangers of UFAI, you do not look away from death or justify it. You realize your own weakness, and the Vast space of possible failures.
And understanding all this, you feel bad about it. Very bad, in fact. You are afraid of the dangers of the future, and you are horrified by the huge amounts of suffering. You have shut up and calculated, and the calculation output that you should feel 3^^^3 times as bad as over a stubbed toe. And a stubbed toe can be pretty bad.
But this reaction of yours is not rational. You should consider the options of choosing not to feel bad about bad things happening, and choosing to feel good no matter what.
Your bad feelings, whether of fear, empathetic suffering, or something else, are probably counterproductive. Not only do you feel bad - a loss of utility in itself - but such feelings probably hurt, rather than help, your efforts to change the world for the better.
You may believe that your emotional outlook must be "rational": that it must correspond to your conscious estimates of the present or the future. Perhaps you expect to die of old age, or perhaps you are aware of people being tortured in secret prisons. You are forcing your emotions to match the future you foresee, and so you feel unhappy and afraid.
I suggest that you allow your emotions to become disconnected from your conscious long-term predictions. Stop trying to force yourself to be unhappy because you predict bad things. Say to yourself: I choose to be happy and unafraid no matter what I predict!
Emotions are not a a tool like rational thought, which you have to use in a way that corresponds to the real world. You can use them in any way you like. It's rational to feel happy about a bleak future, because feeling happy is a good thing and there is no point in feeling unhappy!
Being happy or not, afraid or not, does not have to be determined by your conscious outlook. The only things that force your mind to be unhappy are things like pain, hunger, loneliness, and the immediate expectation of these. If you accept that your goal is to be happy and unafraid as a fact independent of the future you foresee, you can find various techniques to achieve this.
Unfortunately such techniques vary for different people. This post doesn't discuss any: it is about the prerequisite decision to be happy.
Expecting to die of cancer in fifty years does not, in itself, cause negative emotions like fear. Imagining the death in your mind, and dwelling on it, does cause fear. In the first place, avoid thinking about any future problem that you are not doing anything about.
Use your natural defensive mechanisms, such as of not acknowledging unsolved problems, or compartmentalizing different beliefs. Don't dismiss them as biases or irrational practices. They exist for a good reason and have their proper use.
This does not mean that you should ignore problems on the conscious level. It is possible to decouple the two things, with practice. You can take long-term strategic actions (donate to SIAI, research immortality) without acutely fearing the result of failure by not imagining that result.
When you're faced with something terrible and you're not doing anything about it anyway, just look away. Defeat the implicit LW conditioning that tells you looking away from the suffering of others is wrong. It's wrong only if it affects your actions, not your emotions.