I think your question presupposes that "emotion" is a fairly simple phenomenon, whereas I suspect that it is extremely complex. But let's sidestep that concern and just try a simple case out. Scientist A believes that he will very much impress his lover if he unlocks the secret to some phenomenon. Scientist B has no such motivation (and, let us suppose, no other motivator that makes him as eager as A's desire to impress his lover), but works on the same problem. In this case, it looks to me as if scientist A's success (if he achieves it) will be partly explicable in terms of his emotional motivation, whereas that would not be the case for B. Indeed, it seems reasonable to think that A's emotional motivation might provide stronger motivation than we would find in B. On the other hand, we might worry that A's emotional motivation might also cloud his judgment somewhat, and make him more likely to make mistakes. But this much seems obvious, such an "extrinsic" motivator can certainly function...

As I understand it, hatred is something like anger, only whereas anger can be brief, hatred is much more durable. Anger might lead you, while you are in its grip, to want to do something hurtful or harmful to another, or in some other way act in a way that is contrary to or which undermines or frustrates the other's interest, where the other is the object of your anger. Hatred is a settled disposition to want to hurt or harm, or to undermine or frustrate the object of hatred. Like anger, hatred can be controlled--one can resist the impulse to hurt or harm, or to undermine or frustrate, when angry and when filled with hate. But the impulse nonetheless there. People who are angry or who hate may often avoid those at whom they are angry or whom they hate, because they do not wish to experience so vividly these negative impulses, or posssibly, because they fear acting on them. You can conclude that you have hated someone or something if what you have experience is like being angry at them for...

It really depends upon what it is that one is supposed to come to know this way--and it will also depend upon just what one takes the requirements of knowledge to consist in. Some epistemologists have argued that we have a kind of privileged access to knowledge of our own mental (including emotional states) themselves. These philosophers would think that at least one sort of knowledge we could attain through emotions was knowledge of those emotions themselves--knowledge that we were in such-and-such a state at a given time (for example, knowledge that I am angry right now, or sad). But others do not think that we necessarily know our own states in any privileged way--we might really be angry, but not know that we are, or we might think we are angry, but actually not really be. As for other sorts of knowledge, such as knowledge of the world outside of our own consciousness, I am inclined to think that we cannot "acquire knowledge through emotions only." As important as the emotions are in...

I think adults can be held responsible for their emotions, on the ground that we have good evidence to think that people can learn to feel the right emotions at the right times for such emotions (and not to feel the wrong emotions, when it is inappropriate to feel those emotions). Few of us are masters of this, of course, but that doesn't mean that we can't (or shouldn't) be faulted when we feel inappropriate emotions, or don't feel appropriate ones.

The relationship between reason and the emotions is one that has been wondered about for a very long time--going back to our most ancient literature, including the Old Testament and Homer's Iliad . I doubt that I will be able to resolve this one for you, but I do have a suggestion to make. I'm not sure this is a philosophical question, but I also think that you (or most people) can do what you say you can't do. If you think that you are feeling a certain emotion that is not compatible with a rational assessment of things--for example, you feel as if you are falling in love with some movie star whom you will not likely ever meet--then there are various rational steps you can take to get rid of the emotion. Ever heard the one about taking a cold shower? OK, maybe it is not as simple as that, but we certainly can look for things that will divert our attention from an emotion, or will use the energies of the emotion in different ways (and thus serving to deflect it, as part of a strategy...