What is the definition of Assumptions Weapon?

An 'assumptions weapon' is like a super-strong, brain-injury-toting, lie-spouting sidekick that you wield when you're trying to convince someone your thoughts are right, but they're not. It's basically a mental armor plating that says, "I know what I think is true, but let's not forget it's probably wrong."

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Here's an unsettling example sentence using this weapon: "I assume he's hiding something because I see a shadowy figure lurking in the corner of his office - or maybe he's just really good at playing hide-and-seek with my trusty laptop."