The Sophism/Optical Illusion/Paradox Thread

Post your favorite Sophism/Optical Illusion/Paradox and we'll debate/analyze it (and hurt our brains at the same time ).

I'll start:

Answer truthfully (yes or no) to the following question: Will the next word you say be 'no'?

A girl goes into the past and kills her Grandmother. Since her
Grandmother is dead, the girl was never born. If she were never born,
she never killed her grandmother.

1. A Cretan sails to Greece and says to some Greek men who are
   standing upon the shore: "All Cretans are liars." Did he speak the
   truth, or did he lie?
   
2. A week later, the Cretan sailed to Greece again and said: "All
   Cretans are liars and all I say is the truth." Although the Greeks on
   the shore weren't aware of what he had said the first time, they were
   truly puzzled.
   

If someone says "I always lie", are they telling the truth? Or are they lying?

Quote :

A girl goes into the past and kills her Grandmother. Since her
Grandmother is dead, the girl was never born. If she were never born,
she never killed her grandmother.

If we were to apply the theory of disrupting the space/time continuum as proposed by Dr. Emmett Brown, the girl would eventually fade from existance shortly after she killed her grandmother, possibly while playing lead guitar at a high school dance.

However, if the grandmother was aware of the plot to kill her, she could steal the time machine (which could be fashioned from a DeLorean), go forward into the future from the past and makes sure that her daughter never gives birth to the grandmother's would-be killer. This, however, could also have a devestating effect on future events. If the mother's other child, John Connor, sees the effects of time-travel and technology in general, he could have a life-long hatred of computers and machinery, eventually growing up to lead a revolution against our robot overlords.

I think the whole thing is a bad idea.

MetalGuy71 wrote:

Quote :

A girl goes into the past and kills her Grandmother. Since her
Grandmother is dead, the girl was never born. If she were never born,
she never killed her grandmother.

If we were to apply the theory of disrupting the space/time continuum as proposed by Dr. Emmett Brown, the girl would eventually fade from existance shortly after she killed her grandmother, possibly while playing lead guitar at a high school dance.

However, if the grandmother was aware of the plot to kill her, she could steal the time machine (which could be fashioned from a DeLorean), go forward into the future from the past and makes sure that her daughter never gives birth to the grandmother's would-be killer. This, however, could also have a devestating effect on future events. If the mother's other child, John Connor, sees the effects of time-travel and technology in general, he could have a life-long hatred of computers and machinery, eventually growing up to lead a revolution against our robot overlords.

I think the whole thing is a bad idea.

https://www.youtube.com/watch?v=HQiJdf-ebIs

xyz wrote:

was there last week,Nice place

Nice Avatar Quiettype.