"Everything we hear is an opinion, not a fact. Everything we see is a perspective, not a truth." -Marcus Aurelius

I take this as meaning we cannot rely too heavily or trust in our senses. Our senses can deceive us, and for one to simply believe everything they saw and heard would be foolish. Deception runs rampant and ideas are constantly changing. By simply accepting things we perceive to be true, we are limiting ourselves and inhibiting any progress. Facts and truths are indisputable, and for information to reach that state takes far more than simple observation. Ideas must be tested and proven and tested again until there isn't a single doubt in anyone's mind that they are in fact facts and truths. This is how we grow as people and in our knowledge, and how the world progresses.