Existential Fallacy — The Trick You Don't See Coming
Also known as: Existential Instantiation Error
🔥 Hook
"All perfect beings are all-knowing.
Sound familiar? This happens more than you think.
🧠 What's Actually Happening?
The existential fallacy occurs when a categorical syllogism draws a particular conclusion ('some X are Y') from two universal premises ('all X are Y') without establishing that the subject category actually has any members. Universal statements in modern logic do not imply existence -- 'all unicorns have horns' is vacuously true even if no unicorns exist. The fallacy assumes existence without establishing it.
Here's the sneaky part: People naturally assume that categories discussed in an argument have real members. The jump from 'all X' to 'some X' feels trivial, obscuring the implicit existential assumption.
📱 Real-Life Scroll
What you'd see online:
"All perfect beings are all-knowing. All perfect beings are all-powerful. Therefore, some all-knowing beings are all-powerful." (This assumes that perfect beings actually exist; if they don't, the conclusion doesn't follow.)
Another one
'All unicorns have a single horn. All unicorns are magical creatures. Therefore, some magical creatures have a single horn.' (This assumes unicorns actually exist; if they don't, there are no magical creatures with horns to point to, making the particular conclusion unwarranted.)
What it looks like IRL:
Relevant in philosophical arguments about God, ideal forms, theoretical constructs, and any domain where universal claims are made about categories whose existence is debated.
🔍 How to Spot It
Ask whether the subject category actually has confirmed members. If existence hasn't been established, the conclusion drawing on 'some' members is unfounded.
Quick checklist:
- ✓ Is the argument actually proving what it claims?
- ✓ Could I explain this to a friend without it falling apart?
- ✓ If I remove the emotion/pressure, does it still make sense?
💬 What You Can Do
When someone hits you with this, try: "Interesting, but does that actually follow?" You don't need to win. You just need to not get fooled.
🎯 Your Challenge
Find one example of existential fallacy this week. Could be anywhere — a debate, a comment section, a news article, or even your own reasoning. Write it down. The moment you can name it, it loses its power.
Part of the TellDear Teen Book — criticalthinking.guide