The world is so complex and we start out knowing so little. How do we cut the Gordian Knot of our ignorance? Do nothing, just live to be happy and remain blissfully ignorant. This is a very popular option. Another popular approach is to adopt the views of people around us when we are young. In addition, as we encounter other views of things simply adopt the ones that are appealing (they feel good). A third approach is to be ceaslessly curious. This could lead one to observe, think, question. You could study data, conduct thought experiments and read,read,read. (Quality of what you read counts even more than quantity, but that can take time to sort out). One lifetime is barely enough to scratch the surface of a complex world through direct observation alone. Most people reject this approach as being too much work.
Even after intensive study we are still limited to making simplifications. The simplifications may illuminate or obscure further understanding. Starting assumptions are just as important as the line of reasoning that lead to any conclusion. You know the problem, garbage in - garbage out. Actually, different starting assumptions are at the core of many disagreements. Also, once you study an issue intensively enough to draw some firm conclusions, it is good to remember the many accepted truths (scientific and otherwise) replaced what were previously accepted as truths.
Another point worth remembering is that in making simplifications we often reduce ideas into single subjects. That is fine for a first step but in realworld application everything is intertwined. Politics(power), economics, social conditions... all effect and feedback upon each other.
Now on to some specifics. Most human progress does not occur directly from intentional design. As Bret already mentioned, an evolutionary trial and error process is at the heart of progress. Our ancestors were the unwitting guinea pigs who had adopted customs, habits and traditions which enabled them to thrive in favor of groups following other practices. They're practices selected them. This is a notion largely overlooked if not actively rejected by the hyper-rationalistic thinkers of the 18th and 19th Centuries. This misconception is understandable since they were absorbed with rebelling against the traditions and constraints of religion. (They had not yet contemplated Bootism). Think of the strength and robustness of our civilization which has emerged from this process. Everyone in this society benefits from the knowledge of how to live which is embedded in habits, practices and institutions. This is a knowledge gained from the sifting and winnowing of practices over many millenium.
Civilization advances by extending the number of important operations which we can perform without thinking about them. Operations of thought are like cavalry charges in a battle - they are strictly limited in number, they require fresh horses, and must only be made at decisive moments. A.N. Whitehead
An incremental, limited experimental approach to change is an attempt to avoid a major mistake. I'll agree with Bret that the choices of millions of people both in their individual decisions and collectively in the political arena, are less likely to persist in disasterous error than an anoited elite. As for a vision of the anointed, no thanks. Democracy limited by constitutional constraints (assuming a half-way decent construction) is even better at avoiding persistent error. Another way of avoiding the destructive tranny of absolute power is having systems of checks and balances within governmental institutions. Yet another check is to have constraints that cause governmental, commercial, religious and civil entities compete for influence without the ability to totally dominate. My view is that if you do not have a basic understanding of the many facets of power, it's hard to understand the real world. Man is a social animal, but also a political animal.