My cynical view on the heart of man causes me to doubt almost anything I'm told by someone I don't know. My default position is to trust but verify. (Do I need to mention where that quote comes from?)
The way I'd prove anything/everything is to first assume it's incorrect and then work to prove that it is false. There will be a pattern of mistakes, missed calculations, or lies from those who can't be trusted. Once I find that my source is corrupt, I spend no more time believing them, but will then juxtapose their words against sources that can be trusted. Then I can even use the reports of liars to ascertain the truth.
A predictable pattern has emerged from Obama for example. He has become mostly predictable in doing the opposite of what he appears to say. When he says "your taxes won't go up" or "you can keep your doctor" then you can lay money on a safe bet that your taxes are going up and you will not get to keep your doctor.
Democrats have been utterly predictable liars since LBJ. Republicans are less predictable because their stated intent is usually closer to the truth. For example, Bush would tell you what he was going to do; then he would allow the political process to go forward so everyone would be on record. Then he'd do exactly what he said he was going to do, and the Democrats in Congress would act like they didn't support what they just voted for.
Obama will lie about his intent, then use deception/manipulation to accomplish his hidden agenda, and then act like he had nothing to do with the results and blame it on his opposition. The entire leftist enterprise is built on clever liars who are just like their father, the devil.
There have been many times in life where I found out that the truth was not what I thought it was. Though it may have hurt to admit I had been fooled, the only good response is to pivot according to the revealed truth, no matter the cost. It's worse to be betrayed by someone you trusted than to fall for a trick from someone you don't. For example....we've probably all fallen for some girl only to find out later that we're being played. Once you find that out, you can choose to be a fool and ignore reality, or you can walk away hurting.
This explains Democrat and GOP partisans. They can't bring themselves to walk away.
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It is what it is until it isn't