Paradox: Irresistible Force vs. Immovable Object

[lpetrich]

What happens when an irresistible force meets an immovable object?

This is the  irresistible force paradox, Wikipedia's article mentions a Chinese example from the 3rd century BC philosophical book Han Feizi.

In the story, a man was trying to sell a spear and a shield. When asked how good his spear was, he said that his spear could pierce any shield. Then, when asked how good his shield was, he said that it could defend from all spear attacks. Then one person asked him what would happen if he were to take his spear to strike his shield; the seller could not answer.

In doing some research into some Greek mythology, I came across yet another version. The legendary dog  Laelaps (mythology) could always catch what it hunted, while the  Teumessian fox could never be caught.

Some god had sent the Teumessian fox to plague the countryside of Thebes, but that city's regent Creon assigned to Amphitryon the task of getting rid of it. Amphitryon then sicced Laelaps on that fox, and Zeus resolved the paradox of the uncatchable fox and the unavoidable dog by turning both canids into stone, and then into constellations.

Any other interesting statements of this paradox?

 

[Tom Sawyer]

Well, it's not really a paradox. If you have both an irresistable force and an immovable object, all you really have is at least one thing that's mislabelled. Until you bang them into each other, you can't know if your force is an "irresistable" force or a "really tough to resist" force and you can't know if your object is an "immovable" object or a "really hard to move" object.

 

[bilby]

Physics is clear on this - there is no such thing as an immovable object; and ALL forces are irresistible (to objects, that is - two equal and opposing forces can cancel each other out, but that's not what the 'paradox' is talking about).

This 'paradox' can only be a thought experiment; and it isn't a particularly edifying one IMO - if we imagine an immovable object, then it can't be moved, so there cannot be an irresistible force that can encounter it. If we imagine both irresistible force and immovable object, then we are imagining an impossibility, like a square circle. The idea of a square circle isn't worth wasting much time over, and nor is this 'paradox', which is based in the ancients' failure to understand Physical Law. That Law has been known since at least the late 17th Century; anybody who wasted time on it more recently than that is guilty of not doing his basic background research. People who talk of immovable objects may as well discuss the properties of phlogiston, or the reason why nature abhors a vacuum, or why atoms cannot be further divided.

 

[4321lynx]

Physics is clear on this - there is no such thing as an immovable object; and ALL forces are irresistible (to objects, that is - two equal and opposing forces can cancel each other out, but that's not what the 'paradox' is talking about).

This 'paradox' can only be a thought experiment; and it isn't a particularly edifying one IMO - if we imagine an immovable object, then it can't be moved, so there cannot be an irresistible force that can encounter it. If we imagine both irresistible force and immovable object, then we are imagining an impossibility, like a square circle. The idea of a square circle isn't worth wasting much time over, and nor is this 'paradox', which is based in the ancients' failure to understand Physical Law. That Law has been known since at least the late 17th Century; anybody who wasted time on it more recently than that is guilty of not doing his basic background research. People who talk of immovable objects may as well discuss the properties of phlogiston, or the reason why nature abhors a vacuum, or why atoms cannot be further divided.

Or if god can make a stone so heavy that he/she/it cannot lift it.

 

[Tom Sawyer]

Well, if God's omnipotent, he wouldn't have a problem doing that and then also wouldn't have a problem lifting it anyways.