Existential Fallacy: Assuming Existence Without Evidence

What Is the Existential Fallacy?

The existential fallacy occurs in syllogistic reasoning when a conclusion assumes the existence of something, even though the premises do not establish its existence. This fallacy typically arises when a conclusion moves from universal premises (e.g., "all," "none") to a particular conclusion (e.g., "some") without sufficient evidence.

• Structure:

  • Premise 1: All A are B.

  • Premise 2: No C are B.

  • Conclusion: Therefore, some A are not C.

• Problem: Universal premises do not confirm the existence of specific entities, making the particular conclusion invalid.

Examples of the Existential Fallacy

1. Everyday Example:

   • Premise 1: All unicorns have horns.

   • Premise 2: All unicorns are magical.

   • Conclusion: Therefore, some unicorns are magical and have horns.

   • Why It’s a Fallacy: The premises do not establish that unicorns exist, so the conclusion assumes existence without evidence.

2. Scientific Example:

   • Premise 1: All Martian plants are green.

   • Premise 2: All Martian plants photosynthesize.

   • Conclusion: Therefore, some green plants exist on Mars.

   • Why It’s a Fallacy: The premises do not establish the existence of Martian plants.

3. Philosophical Example:

   • Premise 1: All perfect beings are omnipotent.

   • Premise 2: All perfect beings are omniscient.

   • Conclusion: Therefore, some perfect beings are omnipotent and omniscient.

   • Why It’s a Fallacy: The premises do not confirm that perfect beings exist.

Why Is This a Fallacy?

The existential fallacy violates a fundamental principle of syllogistic reasoning:

• Universal premises alone cannot prove the existence of particular entities.

To draw a valid particular conclusion, at least one premise must establish the existence of the subject in question.

How to Avoid the Existential Fallacy

1. Check for Existential Claims in the Premises:

   • Ensure that at least one premise confirms the existence of the entities being discussed.

2. Avoid Jumping to Particular Conclusions:

   • Be cautious when moving from universal premises to particular conclusions.

3. Verify the Logical Foundation:

   • Confirm that the conclusion is fully supported by the premises.

Quiz: Test Your Understanding

1. Question 1:
   Does this argument commit the existential fallacy?

   • Premise 1: All dragons breathe fire.

   • Premise 2: All dragons have wings.

   • Conclusion: Therefore, some dragons breathe fire and have wings.

   • Hint: Do the premises confirm the existence of dragons?

2. Question 2:
   Identify the problem:

   • Premise 1: No aliens are human.

   • Premise 2: All aliens are intelligent.

   • Conclusion: Therefore, some intelligent beings are aliens.

   • Why does this reasoning fail?

3. Question 3:
   Which argument avoids the existential fallacy?

   • A) Premise 1: All dogs are mammals. Premise 2: Some mammals are pets. Conclusion: Therefore, some dogs are pets.

   • B) Premise 1: All unicorns have horns. Premise 2: All unicorns are magical. Conclusion: Therefore, some unicorns are magical.

Conclusion

The existential fallacy highlights the importance of establishing existence in logical reasoning. By ensuring that premises provide evidence for existence, you can avoid this fallacy and construct valid arguments.