Epistemic Status: Reference post. Strong beliefs strongly held after much thought, but hard to explain well. Intentionally abstract.
Disambiguation: This does not refer to any physical good, app or piece of software.
Further Research (book, recommended but not at all required, take seriously but not literally): The Book of the Subgenius
Related (from sam[ ]zdat, recommended but not required, take seriously and also literally, entire very long series also recommended): The Uruk Machine
Further Reading (book): Scarcity: Why Having Too Little Means So Much
Previously here (not required): Play in Hard Mode, Play in Easy Mode, Out to Get You
Leads to (I've been scooped! Somewhat...): Sabbath Hard and Go Home
An illustrative little game: Carpe Diem: The Problem of Scarcity and Abundance
Slack is hard to precisely define, but I think this comes close:
Definition: Slack. The absence of binding constraints on behavior.
Poor is the person without Slack. Lack of Slack compounds and traps.
Slack means margin for error. You can relax.
Slack allows pursuing opportunities. You can explore. You can trade.
Slack prevents desperation. You can avoid bad trades and wait for better spots. You can be efficient.
Slack permits planning for the long term. You can invest.
Slack enables doing things for your own amusement. You can play games. You can have fun.
Slack enables doing the right thing. Stand by your friends. Reward the worthy. Punish the wicked. You can have a code.
Slack presents things as they are without concern for how things look or what others think. You can be honest.
You can do some of these things, and choose not to do others. Because you don't have to.
Only with slack can one be a righteous dude.
Slack is life.
Related Slackness
Slack in project management is the time a task can be delayed without causing a delay to either subsequent tasks or project completion time. The amount of time before a constraint binds.
Slack the app was likely named in reference to a promise of Slack in the project sense.
Slacks as trousers are pants that are actual pants, but do not bind or constrain.
Slackness refers to vulgarity in West Indian culture, behavior and music. It also refers to a subgenre of dancehall music with straightforward sexual lyrics. Again, slackness refers to the absence of a binding constraint. In this case, common decency or politeness.
A slacker is one who has a lazy work ethic or otherwise does not exert maximum effort. They slack off. They refuse to be bound by what others view as hard constraints.
Out to Get You and the Attack on Slack
Many things in this world are Out to Get You. Often they are Out to Get You for a lot, usually but not always your time, attention and money.
If you Get Got for compact amounts too often, it will add up and the constraints will bind.
If you Get Got even once for a non-compact amount, the cost expands until you have no Slack left. The constraints bind you.
You might spend every spare minute and/or dollar on politics, advocacy or charity. You might think of every dollar as a fraction of a third-world life saved. Racing to find a cure for your daughter's cancer, you already work around the clock. You could have an all-consuming job or be a soldier marching off to war. It could be a quest for revenge, for glory, for love. Or you might spend every spare minute mindlessly checking Facebook or obsessed with your fantasy football league.
You cannot relax. Your life is not your own.
Our society even does it to our children. They stay on college and career tracks, fearing one bad grade or mark on their record destroying their whole lives. All is negative selection. Every spare minute is spent padding resumes. In some circles this starts before kindergarden.
It might even be the right choice! Especially for brief periods. When about to be run over by a truck or evicted from your house, Slack is a luxury you cannot afford. Extraordinary times call for extraordinary effort.
Most times are ordinary. Make an ordinary effort.
"You Can Afford It"
People like to tell you, "You can afford it."
No, you can't. This is the most famous attack on Slack. Few words make me angrier.
The person who says "You Can Afford It" is saying to ignore constraints that do not bind you. If you do, all constraints soon bind you.
Those who do not value Slack soon lose it. Slack matters. Fight to keep yours!
Ask not whether you can afford it. Ask if it is Worth It.
Unless you can't afford it. Affordability is invaluable negative selection. Never positive selection.
The You Can Afford It tax on Slack quickly approaches 100% if unchecked.
If those with extra resources are asked to share the whole surplus, all are poor or hide their wealth. Wealth is a burden and makes you a target. Those visibly flush rush to spend their bounty.
Where those with free time are given extra work, all are busy or look busy. Those with copious free time seek out relatively painless time sinks they can point to.
When looking happy means you deal with everything unpleasant, no one looks happy for long.
The Slackless Like of Maya Millennial
Things are bad enough when those with Slack are expected to sacrifice for others. Things are much worse when the presence of Slack is viewed as a defection.
An example of this effect is Maya Millennial (of The Premium Mediocre Life of Maya Millennial). She has no Slack.
Constraints bind her every action. Her job in life is putting up a front of the person she wants to show people that she wants to be. If her constraints noticeably failed to bind the illusion would fail.
Every action is being watched. If no one is around to watch her, the job falls to her. She must post all to Facebook, to Snapchat, to Instagram. Each action and choice signals who she is and her loyalty to the system. Not doing that this time could mean missing her one chance to make it big.
Maya never has free time. There is signaling to do! At a minimum, she must spend such time on alert and on her phone lest she miss something.
Maya never has spare cash. All must be spent to advance and fit her profile.
Maya lacks free speech, free association, free taste and free thought. All must serve.
Maya is in a world where she must signal she has no Slack. Slack means insufficient dedication and loyalty. Slack cannot be trusted. Slack now means slack later, which means failure. Future failure means no opportunity.
This is more common than one might think.
"Give Me Slack or Kill Me" - J.R. "Bob" Dobbs
The aim of this post was to introduce Slack and give an intuitive picture of its importance.
The short-term practical takeaways are:
Make sure that under normal conditions you have Slack. Value it. Guard it. Spend it only when Worth It. If you lose it, fight to get it back. This provides motivation for fighting things Out To Get You, lest you let them eat your Slack.
Make sure to run a diagnostic test every so often to make sure you're not running dangerously low, and to engineer your situation to force yourself to have Slack. I recommend Sabbath Hard and Go Home with my take to follow soon.
Also respect the Slack of others. Help them value and guard it. Do not spend it lightly.
A Final Note
I kept this short rather than add detailed justifications. Hopefully the logic is intuitive and builds on what came before. I hope to expand on the details and models later. For a very good book-length explanation of why lacking Slack is awful, see Scarcity: Why Having Too Little Means So Much.