https://www.pcgamer.com/anthem-will-not-have-offline-play/

While BioWare says we can play Anthem alone, it turns out we can't do so offline. "You need to be online to play," said BioWare's Mark Darrah on Twitter.

That's a disappointment for anyone whose internet connection isn't up to the task, as the person Darrah was responding to indicated. It also reinforces that, while solo play is possible, it is not what BioWare is going for with this one (which is Destiny... it's going for Destiny).