Trust versus prediction

What is the difference between trusting that someone will ϕ and merely predicting their ϕing?

Here are two suggestions that don’t quite pan out.

1. In trusting, you have to have a pro-attitude towards ϕing. But this is false. One can trust a referee will make a fair decision even when one hopes they will make a decision that favors one instead. And you can trust that someone who promised you a punishment will mete it out if you deserve it even if you would rather they didn’t.

2. In trusting, you rely on the person’s ϕing. But this is not always true. A promised benefit might be such that it doesn’t affect any of your actions, but you can still trust you will receive it.

But here is an idea I like. In trusting, you believe that the person will intentionally ϕ as part of her proper functioning, and you believe this on account of the person’s possessing the relevant proper functional disposition. In central cases, “proper functioning” can be replaced with “expression of virtue”, but trust can include non-moral proper function.

A consequence of this account is that it is impossible to trust someone to do wrong, since wrongdoing is never a part of a person’s proper functioning. For trust-based theories of promises, this makes it easy to see why promises to do wrong are null and void: for it makes no sense to solicit trust where trust is impossible.

This account of trust gives a nice extended sense of trust in things other than people. Just drop “intentionally” and “person”. In an extended sense, you can trust a dog, a carabiner, a book, or anything else that has a proper function. This seems right: we certainly do talk of trust in this extended sense.