Pay for an action with only intent from a placed progress cards

Hello,

I assume this is the case but to check: if I have a progress card that generates intent can I use that as the sole source of intent for an action?

The rules originally only say "...influences cards from your hand and/or active items" as being used to pay intent for an action, but then do mention that "different sources can be combined" but stop short of explicitly mentioning if "other sources" can be used on their own.

Thanks,

Robert.