[Nightedge]

-If he's talking about stuff from a source, but the theory is originally proposed by somebody else, does he cite the author or the one who proposed the theory?

Is it correct to use is with originally?

[susan53]

It's nothing to do with the word originally but the fact that the proposal is a past event. So was would be more appropriate here.

But in other sentences originally might well be used with a present verb - eg:

He lives in Sweden but he's originally from Greece

[Nightedge]

Good answer. Thank you.