As long as mankind has been capable of deep thought, there have been those who devoted their lives to rationalizing the world, reality, and everything in general. Among these people there have been several who believed what we perceive through our senses may not be reality.
There are countess ideas on this theory. Some think it may just be our brain distorting what see and feel in order to make better sense of things. Others think our physical world may be entirely an illusion and that we only exist in a spiritual realm. Still others think we've been enslaved by an alien race using our bodies as energy and that our minds have been dumped into some advanced computer system where we live out our virtual lives in the same way we normally live in what most believe to be reality.
Some people sincerely believe this is not the world as it truely is. They think that when you wave your hand in front of your face it isn't really anything in front of your face. They think it's just a mental image sustained by your unwillingness to see the truth because you're far too adjusted to what you've come to know to be reality.
My fellow SDKers, I know some of you have this view. You're frightened by the idea. You desperately want a sign. You need to see if this world is real or not. You need something to hold onto. I'd like to help you with this.
It's often said that in order to truely know what it is you have, you must let it go. Learn the value of what's in your life. If you want to know if what's valuable to you, the money you hold in your hands which embodies physical value, is real or not, then you must let it go.
I know what's real in my life. I know what matters.
If you doubt this world, then send me all of your money and worldly possessions. Once you do that, you'll achieve enlightenment. You'll see you were wrong. Unless I'm wrong. But I'm probably not wrong because I'm not an idiot who believes in the matrix. You're wrong.(Probably)
There are absolute truths, but people frequently confuse opinions with truths because truth is tough to know for sure without knowing EVERYTHING. Basically, anything political is opinion at the level politicians argue. Yet, break down those arguments into their components, like peeling an onion, and you can see truths at the core. Sometimes truths will offend people, so they are rarely brought into the debate. We are a society of placaters and panderers where it is bad to hurt the feelings of others - even if they are doing something wrong. Generally, you know that something is not a truth if it evolves. Truth is absolute, but society takes relative moralistic views, which are not based on truths.