If an immovable object is an object that cannot be moved no matter what and an irresistible force can move anything, what would happen if an irresistible force is used on the immovable object?

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    Why people leve a downvote without an explanation? This is a good startup question. +1 from me
    – jimjim
    Jun 18, 2011 at 22:39
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    This is a common question in introductory logic classes. Imagine if a professor laughed the student out of class for bringing it up. Jun 19, 2011 at 2:50
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    I haven't laughed when a student brought it up, but I always did groan inside. That said, I actually upvoted it, don't see how it can be thought to be "not a real question," and, while not finding it especially interesting as quickly disposed with for the reasons give by @Paul, also think it is clear, and likely of interest to many with an interest in the site.
    – vanden
    Jun 19, 2011 at 6:56
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    @ichiro, @arjang, @frankcrook, @vanden, @paulcalcraft - I cited this question as incorrectly closed in my answer to this question on meta. Please give it a look. Jul 3, 2011 at 13:34
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    @ichiro: This question was closed because it has no context and is based on contradictory premises. As Paul Calcraft writes, it's impossible to have a universe with both something that is unresistable and something that is immovable. This makes the question fall in the category of "not a real question" for all the below items (ambiguity, vagueness, incompleteness, etc.). This is at best Community Wiki material, if indeed this is a common concern on people's minds.
    – stoicfury
    Nov 25, 2011 at 5:53

2 Answers 2


This is an unanswerable question due to contradictory premises.

The immovable object vs. the irresistible force question is a commonly used example for this fallacy of reason, and it is explained on this page:

The problem here is that in a universe where an irresistible force has been defined to exist, there cannot also exist an immovable object, because then the force would not be irresistible. Conversely, if there is discovered or defined such an item as an immovable object, then by definition there can be no such thing as an irresistible force.

  • That is example of a system with contradicting axioms, not definitions. Things can be defined to anything to begin with but only when put together they become contradictory.
    – jimjim
    Jun 18, 2011 at 8:18
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    @Arjang Sorry, I don't quite understand the point you are making. Would you mind rewording or expounding? Jun 18, 2011 at 8:56
  • never mind, the wording of this question is better than the vaiations I had seen before and I had them in mind when I was answering this question. A little variation made a big difference.'
    – jimjim
    Jun 18, 2011 at 23:08

It's a fallacy of reason only if you "assume" that the irresistible force and the immovable object are two separate entities. If they are one and the same, then the statement "they can't meet" holds true. Now, if the universe is the irresistible force and the immovable object, then the logic holds.

  • @Arjang Again the fallacy of reason. I did say they can't collide because it is only one entity. What I am saying is that they can co exists. The other assumption is that a irresistible force moves.
    – user267
    Jun 18, 2011 at 22:49
  • I see your point
    – jimjim
    Jun 18, 2011 at 23:05

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