It has been said that we, as humans, are defined by what we fear. I have found this to be the case. Our beliefs, politics, lifestyles, jobs, associations, and even much of what we buy, is based on what we fear. It is the most basic and primal emotion that we possess. It determines a lot about who we are, and what we will do with and in our lives. If you really think about it, this makes sense. Of the feelings that we normally refer to as emotions, fear is the only one that is truly necessary for the survival of biological organisms (many people wouldn't necessarily include feelings like hunger or lust in the category of emotions; they're too biological and not "emotional" enough). So, one could argue that fear is the original emotion, in the primordial sense of the word.
I once heard a person say that they believed that the most basic and dominant human emotion, the one that determines the most about a person, is love. A fairly idealistic notion, but one must wonder, is it really love that causes most people to do what they do. Is love truly the dominant motivation in getting millions of people up at 7:00 in the morning, to drag themselves to work that they don't particularly like or hate, or is it the fear of what will happen if they don't go. Do you think it's the insatiable love of studying that causes students to do it, or the fear of academic failure? I believe that we've all been in situations where we've been tempted to do something malicious or criminal and didn't. Was this a case of love conquering all? Or could it have, possibly, been the fear of adverse consequences and imminent incarceration that really stopped us?
A person's fear determines a lot about their life, and the topic of social interaction is an excellent example of this. If a person fears loneliness, they're probably not going to spend much time by themselves, and may appear very needy. And if their fear is of public ridicule, then trying to fit in will probably be their preferable course of action. I think it's safe to say that many antisocial individuals display a certain level of fear or apprehension towards other people, (or possibly something else) which helps to determine their behavior. There are also many people, who are often harsh or domineering in temperament, who seem to want some level of recognition from others; but who don't seem to be the least bit concerned with being genuinely liked by others. The root of these people's fear lies within a fragile, but often overblown ego.
I believe that a person's fear is also what determines their beliefs. It seems that many conservative Republicans fear change (this also helps to explain why conservatives are often more radical about religion; churches as well as other places of worship, are some of the only public places which are guaranteed not to change very much). Many liberals, on the other hand, fear tyranny and authority (though it should be noted that they still seek a certain amount of security and are not independent enough to break away from the rest of their political camaraderie). The effect fear has on a person's religious beliefs should be fairly obvious. This often includes not only divine retribution, but social pressures as well.
H.P. Lovecraft once wrote "The oldest and strongest emotion of mankind is fear, and the oldest and strongest kind of fear is fear of the unknown..." and he was right. Fear of the unknown is the very basis for so many of our other fears and the beliefs that follow. From patriotism to prejudice, and haunted houses to changing employers, so much of what we believe, feel and are intimidated by, is based on our fear of the unknown. Everything from an elderly man's fear of change, to a child's fear of the dark, is based on this. And despite many people's claims, that it's best to be open minded and to constantly try new things, fear of the unknown is a natural psychological response designed to keep us alive (this is nature's first priority with everything, and explains why humans as well as other living things can seem so imperfect by many social standards; we're designed for survival first).
I've noticed that many self-help gurus and spiritualists tend to be a little hard on the emotion which we call fear. Many claim to be completely (or at least partially) rid of it. I can't say that I blame them for wanting to cast off their trepidations; fear can be an extremely inconvenient and unpleasant thing. Nevertheless, I would say that they are deluding themselves if they believe that they can exist in a state which is completely devoid of fear. You see, even if they're able to conquer all obvious or easily recognizable fears in their lives, the fact is that their psychological makeup is at least partially founded on fear. It's a major part of the springboard that set them off on their life's journey. They fail to realize (or at least admit), that fear is part of the foundation that their humanity is build on, and is the starting point for wherever there psychological development takes them (many will argue that you have a spiritual side, which is capable of being devoid of fear, but I'm not even going to get into all of the grossly irrational problems with that sort of claim). In that way, the deep, less obvious fears that we possess are inescapable, because they are what make us who we are, and since we can't ever go back, we will always have them in one form or another.
As villains, we must be aware of people's fear in general. The truth is, fear can be an excellent motivator, both for yourself and especially for getting others to do what you want. Many people, who are too petty, stupid or insensitive to appreciate courtesy and rewards, can be easily swayed by fear. This is why governments and religions use it so liberally. It's the only thing that much of the population truly understands. Some knowledge of fear is essential to a true villain (I would say that it's almost as important as a proper level of moral flexibility). This sort of knowledge can also help you to understand and control your own fears as well. Although, some people, in certain situations, can be entertained by their fears, (roller coasters, horror movies etc.) most people try to conceal what they're afraid of, burying it beneath various rationales, self delusions and other emotional camouflage. Your average Joe does not want to admit what really scares him. However, it's not very difficult to determine what a person is afraid of. All you have to do is look at a person, how they live, what they believe and how they interact. Than you can easily figure out what motivates them based on various aspects of their lives. Learn to see an individual for what they truly are, and you shall know what they fear. You will also realize that, for most people, the truth can be one of the most terrifying things of all.