'''TemporalParadox classification''' launched as TemporalParadox: [[http://tvtropes.org/pmwiki/discussion.php?id=s5wyx2c53jqd66dga4jir9sv&trope=TemporalParadox From YKTTW]]

{{Medinoc}}: Well, here we go! I've archived the old page and rearranged it.

{{Yongary}}: Removed
* ''MyMotherTheCar'' has the main character's mom ''reincarnated'' into a 1928 Pierce Arrow.

since it's not actually an example of a time paradox, just a (really stupid) plot device.

'''NOTE: These are the dissussions that were on the old version of these page'''
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RedShoe: Sorry about treading on your toes there, LT. I'm going to wait a few minutes to make sure I don't do it again, then fix it.

LooneyToons: No problem. I didn't know anything of the sort had happened, until I saw this note.

{{Ununnilium}}: I dunno, they seemed more like killer flying time ''dragons''.

RedShoe: While I accept that they are actually not much like monkeys, the phrase "flying killer time monkeys" has gained some popularity on rec.arts.drwho, and as I really like the phrase, I try to do whatever I can to spread it.

{{Ununnilium}}: Ah, objection withdrawn. Flying monkeys deserve more PR.

{{Ununnilium}}: How is bootstrapping not a paradox?

{{Robert}}: It's not self-contradictory. Killing your own grandfather makes your existence a logical impossibility (If you exist, your grandfather died childless. If your grandfather died childless you cannot exist.) Being your own grandfather merely defies common sense, which is not exactly a reliable guide to the possible anyway. It is not a logical impossibility, so not a full blown paradox.

ChromeNewfie: True - you can become your own grandfather if, as the old joke and song goes, you have a son, he marries a woman, and you marry the woman's daughter.

However, ''some'' time travel theories would say that killing your grandfather (before your father was conceived, important caveat) makes your existence a causal impossibility, not a logical one. If you return back to your "own" time, you are identical to an assembly of particles which just happens to look like you and think you should have a father and existence. You may take your headache meds now....

{{Ununnilium}}: Isn't something without a first cause a logical paradox, though?

{{Robert}}: Much debated. Either there is an uncaused cause, traditionally God, or an infinite recess of causes. Both alternatives have been called logical absurdities, by different eminent philosophers. Modern physics takes the view that both are possible - radioactive decay is an event with no cause, and various infinitely old universes would have an infinite recess of causes.

Either way, it's a lesser problem than the outright logical contradiction entailed by the grandfather paradox. We can talk coherently about causal loops, but if you can prevent yourself being born (for real, not some kind of trick) then logic is dead and reason pointless.

(random passer-by): There's an old Larry Niven short story about this idea taken to its logical extreme. I can't recall the name of the story, but the central idea was that if time travel is possible, then time travel will never be discovered. It works like this: let's say that tomorrow, someone builds a time machine and announces it to the world. Sooner or later some crazy person will buy or steal a time machine, and travel back in time to kill the inventor. And if at a later point another inventor builds a time machine, he will suffer the same fate. And on and on, for all sentient species in the universe that discover time travel, forever and ever until the end of time. Any inventor of a time machine will be set upon by a time-traveling madman and killed before he can build it.

{{Seanette}}: Uh, Chrome, would it matter to kill the grandfather before your father is conceived if it's your ''maternal'' grandfather? ;-)
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LooneyToons: I liked the "No, really" at the end of the ''DoctorWho'' example, so I put it back.

{{Kizor}}: You're the super-duper editor, so please yourself. I took it out because I found it funnier deadpan.

LooneyToons: I'm what?

Kizor: I don't know, I'd never use that expression.

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SusanDavis: Split off StableTimeLoop as its own trope, and moved the time loop examples there.

Eternity: The nature of the "temporal paradox" is wholly dependent on the way you want to travel backwards in time. As there are no known ways to do this, the entire subject is rather ambiguous. However, if you do travel back in time, you may not assume that the future you left still exists at all, which is the entire basis for a temporal paradox.
You, the time traveller, now exist outside of the timeline that spawned you. As such, the time you ended up is now "the present" for all intents and purposes. Any grandfather-killing and screwing with the timeline you do reflects on what is happening "now". Just because you have destroyed your own chance to be born does not mean that you no longer exist. You are now a separate entity, much like any other human being now around you. Any travelling into the future you do now-such as by waiting, which is how we all travel into the future-will not reflect the future you know but the future as it will progress with your meddling.
When you time travel, you destroy everything you know and love while you yourself are immune to the effects. Good work.
My point is that time travel should not work as a jump mechanism: "jumping" from one time to another and then "jumping" "back". Indeed, there is no back to the future. The future always lies in front of you. And as for the future you left behind? Well that's gone now.

magic9mushroom: The "Ontological Paradox" category is not a paradox at all, it merely makes people's heads hurt. It all falls under StableTimeLoop.