An Ask MetaFilter question about cooking mustard greens included this note from the poster, on the provenance of their olive oil and their confidence that it was legitimate:

The batch I use all the time, from my 25L can that I got from friends some months ago when my previous 25L can ran out. They press it from olives they grow on their trees, I am *very* confident this is olive juice with nothing added to it.

This led me to muse on "I trust their olive oil is legit" as a level within a levels-of-trust hierarchy. I haven't absolutely worked this out, but maybe some differentiators would be:

1. I trust them to give me change for a $3 purchase without me counting the change they give back.
2. I trust them to watch my coat in a restaurant while I go to the restroom.
3. I trust the olive oil they produce and give me, as a friendly gesture, is genuine.
4. I trust them to watch my laptop in a cafe while I go to the restroom.
5. I trust their advice on what neighborhoods are safe to visit at night.
6. I trust them to stay overnight in my home while I'm there.
7. I trust that, if they say they will do a time-sensitive thing, they'll do it before it's too late.
8. I trust them to clean or stay in my home while I'm not there.
9. I trust them to tell me if they have an infectious disease (or have recently had exposure) before we interact in a way that would expose me to that risk.

And so on and so on, into "take care of me when I am incapacitated" or stuff like that, all the way to things such as "share long-term savings and finances".

It's interesting to think about this. For one thing, I think it's not actually a uniform hierarchy, because people have different skills and capabilities, and I respond contextually to that. Where ought I put "if I tell them a secret, they'll keep it"? Some people can do that but are bad at doing time-sensitive things they've committed to do.

Also, my intuitions listed above are about individual people. What about institutions, or platforms, or devices? I entrust many of those with my security, my property, my data, and my perceptions of reality, beyond the scope of my actual trust. I appreciate Maria Farrell's point about this:

I gave a talk in Austria on smartphones and cybersecurity.

"Put up your hand if you like or maybe even love your smartphone," I asked the audience of policymakers, industrialists and students.

Nearly every hand in the room shot up.

"Now, please put up your hand if you trust your smartphone."

One young guy at the back put his hand in the air, then faltered as it became obvious he was alone. I thanked him for his honesty and paused before saying, "We love our phones, but we do not trust them. And love without trust is the definition of an abusive relationship."

I also do have to make trust decisions with institutional actors. Am I willing to install closed-source software you made on my phone? To believe that your summaries of current events are accurate? To allow you proxy access to data from another platform account? To accept an invitation to speak at your event, thus connecting my reputation with yours? To contract to do work for you? To start even a few hours of work for you before we finalize the signed contract? To buy a durable good that will require an ongoing maintenance relationship with you? To donate money to your political campaign? To provide my legal name, home address, credit card info, and other data when interacting with your service? To buy your commercially produced olive oil?

I don't have even the start of a hierarchy for that, and I suspect it's even less amenable to a single-dimension sequence than the interpersonal stuff is.

It can be so easy for a cautious thought to spiral into "but wait, how do you know THAT" depths. Bootstrapping trust is the kind of problem you can get obsessed with and it can get in the way of doing anything else. The excellent book Lying for Money by Daniel Davies goes into some detail on why -- despite the existence of fraud -- it is necessary for some people or institutions to trust each other for some transactions in order for the logistics of daily life and business to go on without grinding to a halt. And it discusses a food oil fraud! Recommended in case these questions get under your skin or buzz around your brain.