Plausive

With her soft plume (from plausive angels' wing First pluck'd by man)

plausive manners

But the weak have had to put on the armour of cunning to protect themselves from the strong and brutal. […] These plausive manners which recommend you to your fellow-men are indeed a natural mimicry, a putting on, as it were, the mood of those you are among, and the deprecation of the aggression of the strong. For the strong is not only strong but domineering, and it behoves the weak to have these plausive manners as a sure defence.