"The vessel with the pestle holds the pellet with the poison, the flagon with the dragon has the brew that is true."
-The Court Jester
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Of course, the person offering this advice could have been lying.
The point is, trust is essential to human relationships and life. One trusts that people don't lie always, that fast food hasn't been shat on, that gravity works, that this is the real world and not a construct. Trust is inherent to the human psyche. Realize it's important and move on.
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On a related note, buy The Animatrix.