The Human Capacity for Doubt

Skepticism and doubt are worshiped by some as the rational alternative to faith-based belief, but why does doubt go so far sometimes that it prevents people from believing the most basic logical deductions and self-evident claims?

"Plants are green," might be something everyone will acknowledge because it is directly observable, but "plants are green because they reflect green light and thus absorb other frequencies of sunlight" becomes an abstract claim that can't be accepted by some minds.

Someone might be able to see for themselves how prisms diffract sunlight into various color/frequency components, and they might thus be able to understand that the colors they see in objects are reflected, and thus accept the further implication that unreflected colors get absorbed; but some will still question this logic and suspect that there is some other truth that's not within reach yet.

Why is doubt able to undermine the basic capacity for logical reasoning and faith in the conclusions? Is it because we have been subject to so many magic tricks and other manipulations that we learn to doubt even things we would otherwise be wholly convinced of? E.g. when we stare at the pea under the nutshell or the ace moving around with the other two red cards, we learn to distrust even our own eyes. If we can learn to distrust our own eyes, then we can't trust anything . . . right?

So as a result of this cultural/psychological capacity for hyper-doubt (or hyper-skepticism you might call it), a potential arises for manipulation, either through truth, lies, or any combination thereof. And between our capacity to doubt and our capacity to be tricked into suspending doubt in various ways, we become subject to political-economic forces that can defy even the most basic honor of veracity . . . or do they?

What can you believe?