"Women and cats will do as they please, and men and dogs should relax and get used to the idea."
— Robert A. Heinlein

"Love is that condition in which the happiness of another person is essential to your own."
— Robert A. Heinlein (Stranger in a Strange Land)

"Never attribute to malice that which can be adequately explained by stupidity."
— Robert A. Heinlein

"A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, take orders, give orders, cooperate, act alone, solve equations, analyze a new problem, pitch manure, program a computer, cook a tasty meal, fight efficiently, die gallantly. Specialization is for insects."
— Robert A. Heinlein

"When in danger or in doubt, run in circles, scream and shout"
— Robert A. Heinlein

"I am free, no matter what rules surround me. If I find them tolerable, I tolerate them; if I find them too obnoxious, I break them. I am free because I know that I alone am morally responsible for everything I do."
— Robert A. Heinlein

"Progress isn't made by early risers. It's made by lazy men trying to find easier ways to do something. "
— Robert A. Heinlein

"There ain't no such thing as a free lunch."
— Robert A. Heinlein (The Moon Is a Harsh Mistress)

"Anybody can look at a pretty girl and see a pretty girl. An artist can look at a pretty girl and see the old woman she will become. A better artist can look at an old woman and see the pretty girl that she used to be. But a great artist-a master-and that is what Auguste Rodin was-can look at an old woman, protray her exactly as she is...and force the viewer to see the pretty girl she used to be...and more than that, he can make anyone with the sensitivity of an armadillo, or even you, see that this lovely young girl is still alive, not old and ugly at all, but simply prisoned inside her ruined body. He can make you feel the quiet, endless tragedy that there was never a girl born who ever grew older than eighteen in her heart...no matter what the merciless hours have done to her. Look at her, Ben. Growing old doesn't matter to you and me; we were never meant to be admired-but it does to them."
— Robert A. Heinlein

"Once a month, some women act like men act all the time."
— Robert A. Heinlein

"Always listen to experts. They'll tell you what can't be done, and why. Then do it."
— Robert A. Heinlein

"There is no such thing as "Just a cat.""
— Robert A. Heinlein

"Writing is not necessarily something to be ashamed of, but do it in private and wash your hands afterwards."
— Robert A. Heinlein

"Never try to outstubborn a cat."
— Robert A. Heinlein (Time Enough for Love)

"Don't handicap your children by making their lives easy."
— Robert A. Heinlein

"Sex should be friendly. Otherwise stick to mechanical toys; it's more sanitary."
— Robert A. Heinlein

"The most preposterous notion that Homo sapiens has ever dreamed up is that the Lord God of Creation, Shaper and Ruler of all the Universes, wants the saccharine adoration of His creatures, can be swayed by their prayers, and becomes petulant if He does not receive this flattery. Yet this absurd fantasy, without a shred of evidence to bolster it, pays all the expenses of the oldest, largest, and least productive industry in all history."
— Robert A. Heinlein

"Never try to teach a pig to sing.
It's a waste of time and besides it annoys the pig."
— Robert A. Heinlein

"There is no worse tyranny than to force a man to pay for what he does not want merely because you think it would be good for him."
— Robert A. Heinlein (The Moon Is a Harsh Mistress)

"Jealousy is a disease, love is a healthy condition. The immature mind often mistakes one for the other, or assumes that the greater the love, the greater the jealousy - in fact, they are almost incompatible; one emotion hardly leaves room for the other."
— Robert A. Heinlein (Stranger in a Strange Land)

"A dying culture invariably exhibits personal rudeness. Bad manners. Lack of consideration for others in minor matters. A loss of politeness, of gentle manners, is more significant than is a riot..."
— Robert A. Heinlein

"Those who forget their past are condemned to repeat the same mistakes."
— Robert A. Heinlein

"Delusions are often functional. A mother's opinions about her children's beauty, intelligence, goodness, et cetera ad nauseam, keep her from drowning them at birth."
— Robert A. Heinlein

"Sin lies only in hurting others unnecessarily. All other "sins" are invented nonsense."
— Robert A. Heinlein

"One man's theology is another man's belly laugh"
— Robert A. Heinlein

"I never learned from a man who agreed with me."
— Robert A. Heinlein

"How you behave toward cats here below determines your status in Heaven."
— Robert A. Heinlein

"No woman ever ages beyond eighteen in her heart."
— Robert A. Heinlein

"Whenever women have insisted on absolute equality with men, they have invariably wound up with the dirty end of the stick. What they are and what they can do makes them superior to men, and their proper tactic is to demand special privileges, all the traffic will bear. They should never settle merely for equality. For women, "equality" is a disaster."
— Robert A. Heinlein

"Being right too soon is socially unacceptable"
— Robert A. Heinlein

"An armed society is a polite society. Manners are good when one may have to back up his acts with his life."
— Robert A. Heinlein (Beyond This Horizon)

"Climate is what you expect, weather is what you get."
— Robert A. Heinlein

"Be wary of strong drink, it can make you shoot at the tax collector...and miss."
— Robert A. Heinlein (Time Enough for Love)

"Almost any sect, cult, or religion will legislate its creed
into law if it acquires the political power to do so."
— Robert A. Heinlein

"Your enemy is never a villain in his own eyes. Keep this in mind; it may offer a way to make him your friend. If not, you can kill him without hate — and quickly."
— Robert A. Heinlein

"Men rarely if ever dream up a god superior to themselves. Most gods have the manners and morals of a spoiled child. "
— Robert A. Heinlein

"Secrecy is the keystone to all tyranny. Not force, but secrecy and censorship. When any government or church for that matter, undertakes to say to it's subjects, "This you may not read, this you must not know," the end result is tyranny and oppression, no matter how holy the motives. Mighty little force is needed to control a man who has been hoodwinked in this fashion; contrariwise, no amount of force can control a free man, whose mind is free. No, not the rack nor the atomic bomb, not anything. You can't conquer a free man; the most you can do is kill him."
— Robert A. Heinlein

"What are the facts? Again and again and again – what are the facts? Shun wishful thinking, ignore divine revelation, forget what “the stars foretell,” avoid opinion, care not what the neighbors think, never mind the unguessable “verdict of history” – what are the facts, and to how many decimal places? You pilot always into an unknown future; facts are your single clue. Get the facts!"
— Robert A. Heinlein

"In the absence of clearly-defined goals, we become strangely loyal to performing daily trivia until ultimately we become enslaved by it."
— Robert A. Heinlein

"Goodness without wisdom always accomplishes evil."
— Robert A. Heinlein

"The America of my time line is a laboratory example of what can happen to democracies, what has eventually happened to all perfect democracies throughout all histories. A perfect democracy, a ‘warm body’ democracy in which every adult may vote and all votes count equally, has no internal feedback for self-correction. It depends solely on the wisdom and self-restraint of citizens… which is opposed by the folly and lack of self-restraint of other citizens. What is supposed to happen in a democracy is that each sovereign citizen will always vote in the public interest for the safety and welfare of all. But what does happen is that he votes his own self-interest as he sees it… which for the majority translates as ‘Bread and Circuses.’

‘Bread and Circuses’ is the cancer of democracy, the fatal disease for which there is no cure. Democracy often works beautifully at first. But once a state extends the franchise to every warm body, be he producer or parasite, that day marks the beginning of the end of the state. For when the plebs discover that they can vote themselves bread and circuses without limit and that the productive members of the body politic cannot stop them, they will do so, until the state bleeds to death, or in its weakened condition the state succumbs to an invader—the barbarians enter Rome."
— Robert A. Heinlein

"Sex, whatever else it is, is an athletic skill. The more you practice, the more you can, the more you want to, the more you enjoy it, the less it tires you."
— Robert A. Heinlein (The Cat Who Walks Through Walls)

"Yield to temptation...it may not pass your way again!"
— Robert A. Heinlein

"A society that gets rid of all its troublemakers goes downhill"
— Robert A. Heinlein

"Anyone who cannot cope with mathematics is not fully human. At best, he is a tolerable subhuman who has learned to wear his shoes, bathe, and not make messes in the house."
— Robert A. Heinlein

"Live and learn, or you don't live long."
— Robert A. Heinlein (Time Enough for Love)

"My old man says when it's time to be counted, the important thing is to be man enough to stand up."
— Robert A. Heinlein (Between Planets)

"Belief gets in the way of learning."
— Robert A. Heinlein

"Do not confuse "duty" with what other people expect of you; they are utterly different. Duty is a debt you owe to yourself to fulfill obligations you have assumed voluntarily. Paying that debt can entail anything from years of patient work to instant willingness to die. Difficult it may be, but the reward is self-respect.
But there is no reward at all for doing what other people expect of you, and to do so is not merely difficult, but impossible. It is easier to deal with a footpad than it is with the leech who wants "just a few minutes of your time, please—this won't take long." Time is your total capital, and the minutes of your life are painfully few. If you allow yourself to fall into the vice of agreeing to such requests, they quickly snowball to the point where these parasites will use up 100 percent of your time—and squawk for more!
So learn to say No—and to be rude about it when necessary. Otherwise you will not have time to carry out your duty, or to do your own work, and certainly no time for love and happiness. The termites will nibble away your life and leave none of it for you.
(This rule does not mean that you must not do a favor for a friend, or even a stranger. But let the choice be yours. Don't do it because it is "expected" of you.)"
— Robert A. Heinlein (Time Enough for Love)

"There are no dangerous weapons; there are only dangerous men."
— Robert A. Heinlein (Starship Troopers)