I Had a Dream

[Matthaios]

If your friend tells you he caught a fish thiiis big, at least we know fishes have been known to exist and can be interacted with in a stable way.

How do we know that fishes exist? By experience, surely? People had fish-like experiences and, through trust in their perception and the validation of others having (assumedly) similar experiences, came to believe that there are such things as fish, and then the fact that fish exist became common knowledge. Just as with religious experiences, there is a leap from the epistemological (the belief that fish exist) to the metaphysical (that fish exist). Quite a few philosophers (William Alston comes to mind) have argued that experiences of God can be thought of in a similar way.