There is no ignorance, there is knowledge.
There is no passion, there is serenity.
There is no chaos, there is harmony.
There is no death, there is the Force."
In Speculative Fiction, whenever there are two innate forces at work (usually Black-and-White Morality or Order Versus Chaos), the "Light" side (that is, the heroic side) will be transcendent, calm and rational; the "Dark" side (the antagonistic side) will be passionate, impulsive and chaotic. Rarely are the two inversed, with the good side being the emotional one and the evil side being the indifferent.
Related to Villains Act, Heroes React, although that particular trope is more about how the events of the story are motivated by the villain's actions. Also, do not confuse with Ambition Is Evil, in which you can tell the good guys from the bad guys because the bad guys are the one who want to change the Status Quo. This trope is specifically about when there are two metaphysical forces in opposition and one of them motivates through passion and emotion and the other through peace and enlightenment.
- In Naruto, it is later revealed that the Kyuubi (Nine-Tails) gains his power from Naruto's hatred and despair. Or rather, those emotions make it easier for him to take control. Even later, it's revealed that strong emotions are the "curse" of the Uchiha clan, and that feeling strong emotions, then suddenly losing them, is what creates the Sharingan.
- X-Men: Several Face Heel Turns are caused by emotional overload throughout the series—but the most shining example is the Dark Phoenix. This is the explanation for Dark Phoenix—the result of the Hellfire Club feeding decadent and hedonistic desires to the Phoenix Force.
- A frequent theme in the Green Lantern mythos. Especially when the Guardians became despotic and started condemning emotions and the other Lantern Corps turned up as Foils. Essentially, the Green Lanterns are in the "center" of the light spectrum (Willpower) and so they're the most stoic. Red Lanterns and Star Sapphires represent Rage and Love, specifically, and since their colors are on the far ends, their emotions control them. The more powerful the emotion, the more it controls the Lantern.
- Star Wars, of course. The Light and Dark sides of the force tend to play this trope completely straight, although how true this plays out is a case of Depending on the Writer. According to several sources (including George Lucas himself), the Light Side is not merely dull apathy and cold indifference; it's supposed to be all positive synergy and symbiosis that makes the galaxy a better place. Things like love, romance, friendship, and peaceful ambitions are supposed to embody the Light Side just as much as hatred, lust, competition, and violence embody the Dark. This is not how it plays out, normally. One of the main reasons the old Jedi Order fell was because they played this a little too straight, leading to a lot of conflicted feelings in their Chosen One who had let himself fall in love despite it being against the Code and the Order's complete inability to pick up on the signs or help him in any meaningful way. At the end, even Yoda decided that their flawed teachings needed to go. It's no coincidence that a lot of their views seem inspired from Buddhism (however, the latter remains committed to the idea of non-attachment).
- The Skeksis of The Dark Crystal. They inherited the hedonism and violence of the urSkeks, but also their passion, ambition, and general thirst for life.
- The rage-filled Honored Matres from Dune, as opposed to the highly disciplined Bene Gesserit. The Bene Gesserit aren't necesarily a "good" counterpoint though—this is more a case of Black-and-Gray Morality.
- In The Sorceress's Orc, the orcs firmly believe that anger gets in the way of effective fighting. As a result, when the hero befriends an orc, she is way more angry at the racism he is confronted with on a daily basis than he is. Their enemies, all human, are rather more emotional than the orcs.
- Vulcans in Star Trek definitely believe this. Their race happens to have vast emotions which they must completely clamp down, lest they all become raging psychotics. The Romulans are Vulcans who rejected this idea. While antagonistic, they aren't particularly psychotic presumably because they don't bottle up their emotions like their Vulcan cousins.
- In Buddhism, "Dukkha" (suffering) is directly linked to passions such as greed, physical lust and anger. One of the Four Noble Truths is to recognize these as the causes of suffering and take proper action (meditation, moderation, and moral behavior) to correct them.
- Warhammer and Warhammer 40,000: The Chaos Gods are the sum of every sentient being's rage, hope, lust and despair. Worshiped via mass slaughter and warfare, mutation and Chronic Backstabbing Disorder, rape and torture, and spreading disease and pestilence like a demented Santa Claus. The only workable alternative is to cut off the emotions, either by turning the entire world undead (which was one vampire's plan in Warhammer) or by killing everything down to the last bacterium (the Necrons in 40K).
- In its early days, Magic: The Gathering pitted the wise, intellectual Blue and the orderly and moral White colors with the passionate and excessively aggressive Red. Nowadays, while Red still suffers from depictions as a bully, it is definitely by far depicted more heroically thanks to positive attributes like empathy and creativity, while Blue's sociopathic and deceptive traits and White's authoritarian and tyrannical side are both played up.
- In the Street Fighter universe, the Dark Hadou (or Satsui no Hadou in original Japanese) is the surge of violent emotion that drives the nameless martial art used by Ryu, Ken, Akuma, Dan and Gouken. The more fiercely and passionately one fights, the easier it is to become lost to the Satsui no Hadou. According to some sources, merely attempting to use the Raging Demon (Shun Goku Satsu) forever alters the personality of the user and drives them insane. Akuma is the first and only known person to use it and remain some lucidity (although not completely unchanged).
"We're more alike than I'd like to admit."
- Discussed by Jean Grey in Marvel vs. Capcom 3, when she defeats Akuma.
- In the EverQuest series, each god rules over a different physical or emotional domain, and all are clearly defined as Good, Evil, or Neutral. Among the evil gods are Cazic Thule and his daughter Terris Thule, who controls fear and nightmares, and Tholux Paells, the Demi-god of Lust. Among the good gods are Erollisi Marr is the goddess of Love and Quellious the god of Peace and Tranquility. An interesting note is that the extremely evil Rallos Zek, god of War, created Sullon Zek, Demi-goddess of rage and anger. Sullon herself and her domain are considered neutral.
- In The Elder Scrolls series, the primary deities are the Aedra and Daedra. Though both groups are technically beings Above Good and Evil who operate on their own scale of Blue-and-Orange Morality beyond mortal comprehension, the actions of the Aedra toward mortals are usually benevolent, and they are near-universally considered "good" throughout Tamriel. The Aedra embody aspects such as Time, Life, Beauty, Air, etc. - all natural things which have little to do with emotions. The Daedra, for the most part, tend to be much more malevolent toward mortals, and are thus near-universally considered "evil". (Even the more benevolent Daedric Princes, such as Azura and Merida, tend to be Not Nice and do not care about collateral damage in accomplishing their goals.) The Daedra tend to embody ideas like Deceit, Desire, Destruction, Corruption, Ambition, Manipulation, Madness, etc. - things sparked or perpetuated by emotions.