I'm a Utilitarian, which is a moral philosophy that claims that everyone should act in ways that bring the greatest amount of happiness to the most number of people in the world. It is the only moral compass that makes sense for everyone to hold.
Yet many people mistakenly consider Utilitarianism to be immoral or impractical. The biggest concern is that with Utilitarianism, in certain scenarios, people would be willing to do what is typically considered unethical (killing, physically or mentally harming others etc.), because there would be a net increase in happiness.
Utilitarianism is in contrast with another mode of thought, called Kant's Categorical Imperative (I'm not sure why most philosophy has to sound so pretentious). Kant claims that there are certain universal rules that should be followed no matter what, even if it compromises happiness. In doing so, we can ensure that nobody ever does anything immoral.
A classic example to illustrate the difference is: Euthanasia. Say there was someone who was paralysed in bed, suffering every day and preferred to die. A Utilitarian would act 'immorally' in such a case, and say it'd be best to kill that person. But a Kantian would never allow that, because it's a 'universal rule' that all killing is bad.
Yet is the latter really the best solution? I highly recommend watching the 2004 Oscar-Winning Movie, 'Million Dollar Baby'. It gives a heart-wrenching portrait of a female boxing star, Maggie, who was unfortunate to receive an illegal sucker punch in the ring. She falls, hits her head, and becomes a quadriplegic - someone completely paralysed due to injury.
This former sports star is now stuck, suffering in bed and wants to die, she bites her tongue repeatedly in an attempt to bleed to death. Maggie eventually tries to beg her coach to help take her life, which the coach finally agrees to, secretly administering a fatal shot of adrenaline to her.
So in such a scenario, of course it's morally right to kill. Generally taking a life is wrong, but in this case the adult wanted to die, consented to being killed, and would suffer in the world if she continued living. If anything, you're agreeing to torture her if you let the person survive.
Another controversial issue: Suicide. Now I think everyone in the world, no matter how severe their mental issues, can be cured. However some are just unlucky enough to not stumble upon the resources or therapists needed to get better. So if such people are trapped with depression for decades with no escape, it might be best for them to commit suicide.
This is illustrated most clearly by one of, if not the greatest modern writer, David Foster Wallace. He hung himself at age 46.
Here is his quote on suicide: 'Make no mistake about people who leap from burning windows. Their terror of falling from a great height is still just as great as it would be for you or me standing speculatively at the same window just checking out the view; i.e. the fear of falling remains a constant. The variable here is the other terror, the fire’s flames: when the flames get close enough, falling to death becomes the slightly less terrible of two terrors. It’s not desiring the fall; it’s terror of the flames. And yet nobody down on the sidewalk, looking up and yelling ‘Don’t!’ and ‘Hang on!’, can understand the jump. Not really. You’d have to have personally been trapped and felt flames to really understand a terror way beyond falling.'
A Utilitarian would say that hypothetically, if there was a case where slavery created a net good (maybe that's the only way to get enough manpower to fight in a war that determines human fate or something), in that instance slavery should be allowed. Now of course such a scenario never has or probably will ever happen, and that's why Utilitarians say they don't support slavery.
The reason why it's important for everyone to be Utilitarian instead of Kantian, is because it cultivates a mindset of: being willing to adapt.
There have been many ideas that people were sure were inarguably correct, that turned out to be both wrong and harmful (the existence of God, homosexuals are evil, fight for your country first, etc.) And it's the Kantian mindset that leads people to be unwilling to change those beliefs, which is what's leading to many of society's problems we have now.
It's important to possess the willingness to have beliefs you've strongly held for 10, 20, 50 years be challenged, and to change them the moment you find out they are wrong, instead of stubbornly holding on to it and letting both yourself and others suffer.
Whenever science, or whatever new medium we discover that better defines truth, ever disproves our long-held beliefs, be sure to be flexible enough to adjust. Because truth is always important than dogma, and truth will set people free
Specific: What is Objective? What is Subjective?
Related: Everyone Should Have a Free House