Clifford Donald Simak is a well-known ScienceFiction writer. His most famous novels are ''City'', ''The Goblin Reservation'' and ''Literature/WayStation''; his short story "Huddling Place" appeared in ''The Science Fiction Hall of Fame, Volume 1''.

His works tend to be soft according to MohsScaleOfSciFiHardness, as he's concentrating on characters and story, not on tech, but he doesn't [[YouFailPhysicsForever fail physics forever]]. He tends to be more idealistic than cynical.

What can be said in addition? Let's just say that Creator/IsaacAsimov was his AscendedFanboy.

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!!The author's works provide examples of:
* AllMythsAreTrue: The premise of the novel ''Out of Their Minds''.'
* AlternateSelf: ''The Goblin Reservation''
* BackupTwin
* BlueAndOrangeMorality: In ''City'', not only the ants are inscrutable, but the person responsible for the dawn of their civilization, Joe, a telepathic mutant, is also an example. This is actually the point of his character: he does not want to [[MessianicArchetype save]] or [[BewareTheSuperman subjugate]] humankind, he just does not wish to encounter them, and does not value the very concept of society.
* ClarkesThirdLaw: ''The Goblin Reservation'' plays it straight. Magical creatures turn out to have been engineered by SufficientlyAdvancedAliens.
* CloningBlues: Duplicates in ''Good Night, Mr. James'' are treated as legally and morally expendable. [[spoiler:[[TomatoInTheMirror The main character's a duplicate]].]]
* CosyCatastrophe: Humanity's fate in the ''City''. Human civilization simply lived its course and ended slowly and (relatively) peacefully.
* CreatorProvincialism: Simak often set his stories in Millville, where he was born.
* CreatorThumbprint: Many.
** JustOneSecondOutOfSync, especially if it's used to create alternative Earths.
** The hero, the love interest, the nonhuman sidekick and a bunch of loonies go on a quest, loonies gradually vanish from the party for reasons directly connected to the reason they went on a journey in the first place, yadda yadda yadda, happy ending, true love, and some mystical higher forces were behind all this.
** Goblins. He has a very interesting interpretation of goblins as magic eldritch abominations from other dimensions or planets, with reasons unknown, and morality radically different, and logic that will never be understood by us humans.
** Different biological lifeforms [[BizarreAlienLocomotion with wheels]] feature in ''The Goblin Reservation'' and several short stories. (In most cases, it's evidence they've been engineered).
* EarthThatUsedToBeBetter: ''City'''s main theme is the decline and fall of humanity, so there's plenty of the examples along the way. Eventually the earth reverts to its original state, but its masters are now [[StarfishAliens sentient, industrious and incomprehensible Ants]], and what will happen to it is a question.
* HumanityIsSuperior: Inverted. Humanity is a young race, if other alien races are adults then humanity is in kindergarten, and going to "school" is one of his favorite plots.
* HumansAreSpecial: ''Literature/WayStation'' and other stories.
* {{Immortality}}: Jenkins, the immortal robot in the ''City'', whose fate is to see the twilight of Humanity.
* KillAndReplace: ''Good Night, Mr. James''. [[spoiler:The duplicate succeeds in killing the original, but finds out that [[ShootTheShaggyDog he was poisoned immediately after he was made]].]]
** This ending was [[LighterAndSofter softened]] when the story was adapted for the original ''Series/TheOuterLimits'' as "The Duplicate Man": [[spoiler:The duplicate still dies, but the original not only survives, but becomes a better person because the duplicate reminds him of his younger, more idealistic self.]]
* MergingMachine / TeleFrag: Mentioned to have happened in ''The Goblin Reservation''.
* NecessarilyEvil: Humanity in ''Skirmish''. All human development has been based upon synthetic technology of some kind, and thanks to InstantAIJustAddWater, people must either revert to savagery or knowingly enslave an entire species. (LamarckWasRight isn't an option here--even a ''sewing machine'' comes to life.)
* NoTranshumanismAllowed: Averted for good in ''City'', which eventually brought humanity's downfall. Humans were initially baffled by unexplained disappearances of scientists, transformed to survive the conditions on Jupiter, until one of them finally returned. It happened that the life of the transformed being was so much ''better'', that most people simply left the Earth and their humanity.
* OldRetainer: For possibly the '''Oldest''' OldRetainer ever, we have Jenkins, the robotic butler in ''City''.
* OurDragonsAreDifferent: ''The Goblin Reservation''.
* OurGhostsAreDifferent: ''The Goblin Reservation''.
* OurGoblinsAreDifferent: Very different. They are the FairFolk, for one. And they aren't evil, they are just... well, ''really'' alien.
* PsychicPowers: ''Time is the Simplest Thing'', ''Ring Around the Sun'', the BigBad in ''The World of the Red Sun''...
** Also, in his first story, ''The World of the Red Sun'', the main characters place the TimeMachine on a plane to avoid being {{TeleFrag}}ged by mountains or buidings.
* ReligiousRobot: In ''Message From The Stars'', the humans have [[{{Transhumanism}} transcended their physical forms]], casting aside their old religions as well as as the robots that used to serve them. Having lost the purpose of serving mankind, the robots have instead turned to Christianity. It is implied that their theological discourse will gradually turn Catholicism into a RobotReligion, just like Afro-American churches tend to have a black Jesus on the cross.
* StarfishAliens: IN SPADES.
** In ''The Goblin Reservation'' we have Wheelers, each of them is a hive of sentient worms in a bag on two wheels using a biological equivalent for a rocket engine to move around. Some aliens, like the Wailer in ''Special Deliverance'', [[EldritchAbomination are just incomprehensible]].
** Ants in the ''City''. They simply ignore everyone else, forcing remaining humans and [[UpliftedAnimal dogs]] to leave the Earth for good.
* TeleportersAndTransporters: ''The Goblin Reservation''
* TimeTravel: a number of them, starting from his first short story. Note that in most of his works the timestream can't be changed, a human being can be an observer of the past at most. [[spoiler: This tradition dates from his first story, too]]
** In ''City'' the time travel is impossible -- the time there is a string of {{Alternate Universe}}s moving through it, so any attempt of time travel will simply bring you to parallel world.
* {{Twinmaker}}: ''The Goblin Reservation''.
* WitchHunt: In ''Time is the Simplest Thing'', witches are people with PsychicPowers. Some of them actually fly on brooms if they want to.
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