Behind these two isms lie the source of much conflict in the world today. Is it better to aim high, and not reach, or to aim at average and reach it? Is it better to be good or fair? Is it better to be optimistic or pessimistic? There are several branches in each of these categories, and no one side can be proven to be right in all branches. But what exactly is idealism and realism, and why do they matter?
The definitions of the two words should be obvious, but for clarity sake, they are given here. Idealism, according to the American Heritage Dictionary of the English Language, means "The act or practice of envisioning things in an ideal form." In simpler language, it means to aim for perfection. On the surface, it sounds nice, but all this ignores the basic human trait, the one shared across cultures, languages, and races: imperfection. To be human is to be errant. Thus, the dreams of idealists often get dashed and projects they attempt often end either in failure or at least "less than they could have been."
On the other hand, realism means "the inclination towards literal truth and pragmatism" (ibid). It also means to accept life the way it is, and favour the practical method of dealing with it. This too seems to be a good trait on the outside, but it has some flaws. To only aim for average cuts short the potential of humanity. Just because humanity isn't perfect does not mean it cannot reach excellent every now and then.
There are significant contrasting plus sides to both. To be an idealist is to reach for the stars. However, idealists often become lost in their dreams, and forget the real world around them; and as a result can acquire an out-of-touch aura about them. Realists on the other hand are more grounded in reality (hence the name), and as a result are often better prepared to deal with it. However, as they focus too much on reality, they often aim lower than can be reached, only aiming for what can be reached with assurance, and as a result often miss out on the few times humanity does reach excellence.
How does this apply to our world? Several ways!
You have the old optimist-pessimist, is-the-glass-half-full-or-half-empty argument that rather nicely sums this whole thing up. However, most of the attention often gets focused on the studies that show how optimists live longer than pessimists. I have never heard a study as of yet that shows how pessimists are likely safer from robbery, murder, and other crimes, as a result of extra precautions taken. Plus, this whole thing is really only one branch of the issue.
Also tied together in this debate is the whole issue of whether it is better to be "good," as defined in the Christian, caring sense, or to be fair. Justice versus grace: what is the answer? Ideally, all people have the potential to be good inside of them, and so we should never give up on a person by sentencing them to death for a heinous crime. However, realistically, there are some people that will never change, and sometimes mercy is violated and thrown in the face of the giver. What then is the correct solution?
Two schools of political thought have emerged in the last few centuries that have differing solutions to this problem. The conservative belief is in justice, fairness, and equality in all matters of life. Break the law, and you should have to compensate the person that you injure. The all-important virtue of conservatives is fairness. In all things, justice must prevail, or else the society is flawed. All people should always get what they deserve, and all people should always be treated the same way. As all people through action expose that which is within, then all people should be judged by their actions, and be treated accordingly.
The liberal belief, in contrast, is in goodness, mercy--and equality, but not in the conservative sense. For liberals, all people are intelligent, and therefore don't act a certain way without a reason. It is then up to us as members of society to discover that reason and work to heal the criminal's wounds, in order to help them to become a productive member of society again. The all-important virtue of liberals is understanding, leading to goodness. All people should be treated 'fairly,' in the sense that if they had a bad childhood or because of circumstances beyond their control receive poverty wages, they should be compensated, so that all people may enjoy life equally.
Both sides do have a legitimate point. It is always important to be just and fair. Failing to be fair leads to favouritism, and when favouritism is introduced into the political arena, you get corruption, and surely I don't need to explain why that is bad for a political system, especially a democracy. Being fair means that people will get what they work for; the hardest working person will end up the richest, and the homeless guy down the street who failed all his math tests in high school will end up the poorest. Everyone gets precisely what they deserve.
Just as important is to be good every once in a while. Not everyone who is at the bottom of the heap is there by their own actions, but often they are there due to someone else's negligence. A second point is that all people are fallible--it is human nature to make mistakes. Someone who goes through thirty years of perfect driving shouldn't lose their license for an accidental driving infraction. Every now and then, someone comes up in a court of law who is a good person who just made one bad mistake. To facilitate good, we must understand people. It is the liberal belief, the optimist's belief that all people are rational; but things happen along the way--a run-in with the wrong crowd, inexperienced parents--and they end up on the wrong side of the law. (Breaking the law is obviously not rational.) Therefore, the belief also includes that all people are fixable.
Neither of these does well standing alone. The system that completely operates on justice and justice alone will end up punishing people who, if left alone, would have continued to contribute to society until they had died of old age. A completely just system will nail good people who make a mistake. And based on the accepted premise that all humans are imperfect, all humans will eventually fall short of the law. Can you punish an entire society by its own laws?
At the same time, understanding why someone shot his neighbour dead doesn't make it right, nor is it just to the deceased. Also, sometimes a smart-alec will take advantage of someone trying to help them and tell them lies, tell them what they want to hear, so that they can be "understood" in such a manner as will facilitate their own escape back into the world, where they will repeat their past crimes. There are some, regardless of how they got there, who cannot be helped. Obviously, a balance between conservatism and liberalism is necessary.
Of all the justice vs. goodness debates, none can be bigger than the one God must deal with. That said, God being God, He certainly has it perfect, answering to the calls of justice from Satan while still being merciful to mankind. God is neither conservative or liberal. For God, the correct balance between justice and grace is not a question, but a foregone conclusion, for God doesn't change. Humans, being inferior in several respects, seem only to be able to grasp one of these concepts at a time, and so we split up into respective parties when it comes to politics, and have heated debates and arguments whenever an election approaches.
Currently, our political system works. Legislative houses are generally split somewhere near the 50-50 line between liberals and conservatives; each acts as a check on the other. Often, this leads to stalemate, and little progress is actually accomplished; other times, the control of the majority passes from one to the other every few years, and a weaving, but neutral path is followed. This works--a fine line, a balance between justice and goodness is established. That said, the system is never perfect--only God is perfect--but it is generally good enough to allow for civility to flourish, for ethics to be followed, and for hope to be found among the lower classes.
The liberal ideal, that of fixing all broken people, of a perfect society where all people are equal in riches and workload, and where people get exactly what they deserve because they all deserve well, may not be possible (admittedly, it is probably impossible), but just because there is little chance of success does not mean you shouldn't try. Failure is not a foregone conclusion! Many people in ages past have found it better to expend yourself heroically in a worthwhile but impossible cause. That said, the realism conservatives bring is a necessary temper to dreams. Being familiar with present situations is important to knowing how to properly navigate through them. Knowing the way of the world is important to survival, and necessary to have any form of success.
Which do you prefer?