ad. Not falsifiably, based on available facts and general knowledge.
the GNU version of the Collaborative International Dictionary of English
ad. In a plausible manner.
ad. Contentedly, readily.
The Century Dictionary and Cyclopedia
In a plausible manner.
With fair show; speciously; so as to command attention or win approbation.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
ad. easy to believe on the basis of available evidence
Word Usage
"The moral order is what structures and orders the otherwise baffling spiritual world, and it is the genius of Charles Williams to have shown it with a certain plausibly, exploring the implications in a satisfactory way."