P.S. In Greek, 'I know' is 'oida'. Although this is semantically present 'tense', its form is that of the perfect 'tense' of the verb 'to see'. So in Greek, 'I know' explicitly means 'I have seen'.

There you go, that was more fun for a discussion of knowledge as a concept :)

(Scare quotes for 'tense' because it's a complex concept!)